Friction Welding: Practical Examples and Case Studies

Low-Temperature Friction Welding of Aluminum-Copper Transition Joints

For aluminum-copper transition joints with diameters of 8-50mm, low-temperature friction welding is commonly used to eliminate the brittle alloy layer and oxide film in the aluminum-copper joint. This is achieved by reducing the rotation speed, increasing the friction and forging pressures, and keeping the welding temperature below the aluminum-copper eutectic point of 548°C.

The welding parameters can be found in Table 4-10. To prevent aluminum loss during welding and bending deformation caused by compression instability of the aluminum-copper specimen, a mold, as shown in Figure 4-17, is used for heating the aluminum-copper. Low-temperature friction welding allows for control of the friction surface temperature within 460-480°C.

This ensures sufficient plastic deformation and promotes ample diffusion between aluminum and copper atoms, without producing brittle intermetallic compounds. Consequently, the joint has high mechanical properties and good thermal stability.

Due to the high strength, plasticity, and toughness of the joint, circular cross-section joints can be forged into various shapes and sizes as needed, expanding its application range. The main production steps of the transition joint include cutting, annealing, welding, deburring, drilling, forging, shaping, and surface cleaning.

Table 4-10: Welding Parameters for Low-Temperature Friction Welding of Aluminum-Copper

Joint Diameter/mmRotation Speed/(r/min)Friction Pressure/MPaFriction Time/sUpset Forging Pressure/MPaDie Outer Allowance/mm
AluminumCopper
Φ610301406600110
Φ105401706450213
Φ163202006400218
Φ202702406400220
Φ262082806400222
Φ301803006400224
Φ361703306400226
Φ401603506400228
① The protrusion of aluminum-copper parts outside the die mouth.

Friction Welding of High-Speed Tool Steel to 45 Steel

Friction welding of high-speed tool steel to 45 steel has been widely adopted in the national tool industry, replacing flash welding due to its clear advantages in terms of welding quality, energy consumption, and environmental hygiene.

Because high-speed tool steel has high-temperature strength and low thermal conductivity, and 45 steel has poor high-temperature strength, during friction welding, to prevent 45 steel deformation and loss, and to prevent high-speed tool steel from cracking, the 45 steel workpiece must be enclosed and pressurized using a mold as shown in Figure 4-18.

At the same time, the friction pressure and upset pressure should be increased, the friction time extended, and the joint should be immediately heat treated and annealed after welding. The welding parameters for friction welding of high-speed tool steel to 45 steel can be found in Table 4-11.

Figure 4-17 Schematic Diagram of Aluminum-Copper Friction Welding
  • 1 – Copper workpiece
  • 2 – Aluminum workpiece
  • 3 – Mold
  • n – Rotational speed of the copper workpiece
  • F – Axial tool
  • v – Feed rate of the moving chuck
Figure 4-18 Schematic Diagram of High-Speed Tool Steel to 45 Steel Friction Welding
  • 1 – High-speed tool steel
  • 2 – 45 Steel
  • 3 – Mold

Table 4-11 Welding Parameters for Friction Welding of High-Speed Tool Steel to 45 Steel

Joint Diameter
/mm
Rotation Speed
/(r/min)
Friction Pressure
/MPa
Upset Forging Time
/s
Upset Forging Pressure
/MPa
Notes
14200012010240Using Mold
20200012012240Using Mold
30200012014240Using Mold
40150012016240Using Mold
50150012018240Using Mold
60100012020240Using Mold

Friction Welding of Boiler Serpentine Tube

In boiler manufacturing, to conserve energy, serpentine tubes made of 20-steel, with a diameter of 32mm and a wall thickness of 4mm, are commonly produced using friction welding. During welding, as the tube length reaches about 12m, challenges such as stable tube rotation, consistent welding quality, and reduction of internal burrs need to be addressed.

To improve and stabilize the welding quality of the serpentine tubes and minimize the internal burrs, a strict friction welding process is adopted.The welding parameters for the serpentine tubes are listed in Table 4-12. The welding process uses peak power control, followed by a quick stop and rapid upset forging.

With these parameters, the welding joints have minimal internal burrs, short and thick burr shapes both inside and outside, and smooth and flat surfaces. The tensile strength of the joints reaches 510~550MPa, and all mechanical performance tests result in breaks occurring on the base material.

The metallographic structure of the joints indicates that the weld zone consists of fine-grain sorbite and ferrite structures, with no defects found, enhancing joint longevity. In a sample of 3% taken from hundreds of thousands of welded joints, all were found to be satisfactory.

Table 4-12 Welding Parameters for Friction Welding of Serpentine Tubes (Diameter: 32mm, Wall Thickness: 4mm)

Rotational Speed / (r/min)Friction Pressure / MPaFriction Time / sUpsetting Pressure / MPaJoint Deformation Amount / mmNote
14301000.822002.3 – 2.4Controlled by peak power.

Friction Welding of Petroleum Drill Rods

Petroleum drill rods, essential tools in oil drilling, are welded together from a threaded tool joint and a pipe body. The material for the tool joint is 35CrMo steel, and the pipe body is made from 40Mn2 steel. The common welding cross-section sizes for these drill rods are Φ140mm×20mm and Φ127mm×10mm.

For the friction welding of these large cross-sections and long pipe joints made from low-alloy dissimilar steels, a large welding machine is required. To reduce the friction heating power, especially the peak power, we employ weak standard welding. The parameters for this method of friction welding are outlined in Table 4-13.

To eliminate the internal stress after welding, improve the metallographic structure of the weld seam, and enhance the performance of the joint, post-welding heat treatment is necessary.

Table 4-13: Friction Welding Parameters for Petroleum Drill Rods

Joint Size
/mm
Rotational Speed
/(rpm)
Friction Pressure
/MPa
Friction Time
/s
Upsetting Pressure
/MPa
Joint Deformation Amount
/mm
Notes
Φ140×20                 Φ127×105305~630~5012~14Friction Deformation: 12mm,                 Upsetting Deformation: 8~10mmDrill Rod Tool Joint             Chamfering of Welded End Surface

Linear Friction Welding of Resin-Based Pipes

In recent years, with the development of thermosetting resin materials, resin-based pipes have been increasingly used in urban construction, petrochemical industries, and others, highlighting the issue of connection. For the on-site installation of large pipes, linear friction welding can be employed.

Using a vibratory clamp to create friction between the surfaces to be welded, the process stops as soon as the temperature suitable for bonding is reached and upsetting pressure is applied to achieve welding. The main parameters of linear friction welding for resin-based pipes are vibration frequency, amplitude, and upsetting pressure.

For pipes with an outer diameter of 216mm and a wall thickness of 16mm, a vibration amplitude of about 1mm can be chosen during welding, and the vibration frequency should be below 15Hz.

The resulting joint yield strength can reach over 20MPa, nearly the same as the parent material strength, and the elongation rate reaches 72% of the parent material elongation rate.

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