tailieunhanh - Advanced Welding Processes Episode 1 Part 2

Tham khảo tài liệu 'advanced welding processes episode 1 part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | An Introduction to Welding Processes 5 b Cold pressure welding If sufficient pressure is applied to the cleaned mating surfaces to cause substantial plastic deformation the surface layers of the material are disrupted metallic bonds form across the interface and a cold pressure weld is formed 3 . The main characteristics of cold pressure welding are i the simplicity and low cost of the equipment ii the avoidance of thermal damage to the material iii most suitable for low-strength soft materials. The pressure and deformation may be applied by rolling indentation butt welding drawing or shear welding techniques. In general the more ductile materials are more easily welded. This process has been used for electrical connections between small-diameter copper and aluminium conductors using butt and indentation techniques. Roll bonding is used to produce bimetallic sheets such as Cu Al for cooking utensils Al Zn for printing plates and precious-metal contact springs for electrical applications. c Friction welding In friction welding a high temperature is developed at the joint by the relative motion of the contact surfaces. When the surfaces are softened a forging pressure is applied and the relative motion is stopped figure . Material is extruded from the joint to form an upset. The process may be divided into several operating modes in terms of the means of supplying the energy 1 Continuous drive in which the relative motion is generated by direct coupling to the energy source. The drive maintains a constant speed during the heating phase. 2 Stored energy in which the relative motion is supplied by a flywheel which is disconnected from the drive during the heating phase. The process may also be classified according to the type of motion as shown in figure . Rotational motion is the most commonly 6 Advanced Welding Processes used mainly for round components where angular alignment of the two parts is not critical. If it is required to achieve a fixed relationship