HEAT BALANCE

Heat Balance Lesson Objectives When you finish this lesson you will understand: Factors Effecting Heat Balance Solve Heat Balance Problems Learning Activities 1.View Slides; 2.Read Notes, 3.Listen to lecture 4.Do on-line workbook Keywords: Heat Generation, Heat Conductions, Electrode Geometry, Resistivity, Thermal Conductivity

Factors Affecting Heat Balance Relative electrical and thermal conductivities of the metals to be jointed Relative geometry of the parts at the joint Thermal and electrical conductivities of the electrodes Geometry of the electrodes

Factors affecting uniform distribution of heat are : Projection design and location. Thickness of the section. Thermal and electrical conductivities. Heating rate. Electrode alloy. Heat Balance in Projection Welds

After 20% welding time At the end of welding time Temperature Electrode Workpiece Temperature distribution at various location during projection welding. Temperature Distribution

Heat Dissipation Weld Nugget Water-Cooled Copper Alloy Electrode Base Metal

Improving Heat Balance Methods for Spot Welding (a)(b)

Improving Heat Balance Methods for Spot Welding High Conductivity Alloy High Resistance Electrode High Conductivity Alloy Low Conductivity Alloy Low Conductivity Alloy (a) (b)(c) (d)

Edge distance Joint overlap Weld spacing Joint accessibility Dissimilar thickness Joint Design

Crossed wire products such as refrigerator racks, grills of all kinds, lamp shade frames, wire baskets, fencing etc. are made by projection welding. The most common metal welded is LC steel. Cu-Ni alloys are also welded using projection welding. Process Applications

Typical Mill Forms and Products of Upset Welding [Reference: Welding Handbook, Volume 2, p.600, AWS]