1. Heat Balance

2. Lesson Objectives When you finish this lesson you will understand: heat flow thickness & material conductivity effects Recommended heat flow practices in spot & flash welding Learning Activities 1.View Slides; 2.Read Notes, 3.Listen to lecture 4.Do on-line workbook Keywords ConductionConvectionRadiationThermal conductivity Electrode Face

3. 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

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

5. 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)

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

7. Resistance Weld Manual, 1972

8. A heat balance problem is set up when welding Steel to Aluminum Using a Transition Material of Roll Bonded Al to Steel Sheet. Heat Balance Steel Aluminum Steel-Al Transition Move to Next Slide to See Nugget Growth

9. Results and Discussion (nugget development model) Steel Al One CycleTwo CyclesThree CyclesFour CyclesFive CyclesSix CyclesSeven CyclesEight CyclesNine CyclesTen CyclesEleven CyclesTwelve Cycles

10. Resistance Weld Manual, 1972 Low High

11. Resistance Weld Manual, 1972

12. Resistance Weld Manual, 1972

13. Turn to the person sitting next to you and discuss (1 min.): We have seen that there is a heat balance problem when thick and thin steels are welded. What do you think will happen when we try to weld thick and thin copper sheets?