This set of Manufacturing Processes Question Paper focuses on “Laser Welding – 3”.
1. How many types of welding modes are there in laser beam welding?
Explanation: There are typically three types of welds:
– Conduction mode
– Conduction/penetration mode
– Penetration or keyhole mode.
2. Conduction mode welding is performed at _____ energy density.
Explanation: Conduction mode welding is performed at low energy density forming a weld nugget that is shallow and wide. Conduction/penetration mode occurs at a medium energy density and shows more penetration than conduction mode.
3. The penetration or keyhole mode welding is characterized by ______
a) shallow welds
b) narrow welds
c) irregular welds
d) nuggets of welds
Explanation: The penetration or keyhole mode welding is characterized by deep narrow welds. This direct delivery of energy into the material does not rely on conduction to achieve penetration, and so minimizes the heat into the material and reduces the heat affected zone.
4. In penetration mode, a filament of vaporized material formed by laser light known as a _____
Explanation: In this mode, the laser light forms a filament of vaporized material know as a “keyhole” that extends into the material and provides conduit for the laser light to be efficiently delivered into the material.
5. In conduction welding, the laser beam is focused to a power density of order of _____ W/mm2.
Explanation: Conduction joining describes a family of processes in which the laser beam is focused:
– To give a power density on the order of 103 W/mm2
– It fuses material to create a joint without significant vaporization.
6. Conduction welding has _____ modes.
Explanation: Conduction welding has the following two modes:
– Direct heating
– Energy transmission.
7. The first conduction welds were made using _____ lasers.
c) polymer lasers
d) semiconductor lasers
Explanation: The first conduction welds were made in the early 1960s, using low power
• pulsed ruby lasers, and
• CO2 lasers for wire connectors.
8. In direct heat conduction welding, heat flow is controlled by a conventional thermal conduction method.
Explanation: During direct heating, heat flow is governed by classical thermal conduction from a surface heat source and the weld is made by melting portions of the base material.
9. Conduction welds can be made in a wide range of metals and alloys in the form of wires and thin sheets.
Explanation: Conduction welds can be made in a wide range of metals and alloys in the form of wires and thin sheets in various configurations using
– CO2, Nd-YAG and diode lasers with power levels on the order of tens of watts
– Direct heating by a CO2 laser beam can also be used for lap and butt welds in polymer sheets.
10. Transmission welding is used for joining _____
a) aluminium alloys
b) cast iron to wrought iron
d) components made of copper
Explanation: Transmission welding is an efficient means of joining polymers that transmit the near infrared radiation of Nd-YAG lasers and diode lasers.
Sanfoundry Global Education & Learning Series – Manufacturing Processes.
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