oxyacetylene welding

3. Welding Mild Steel Mild steel is the easiest to gas weld. If done properly welds have good integrity. Lack of porosity Oxides Or other defects The secondary flame in gas welding shields the molten pool from the air, which would cause oxidation.

4. Factors Affecting Weld Quality Torch Tip Size Used to control weld bead width, penetration, and speed. Tip sizes must be changed to suit the thickness of the metal being welded. Do not lower flame temperature, this will cause the tip to overheat and possibly cause backfire and flashback.

5. Factors Affecting Weld Quality Torch Angle Affects the speed of melting and size of the molten pool. The ideal angle is 45° As the angle approaches 90° the rate of heat increases and visa-versa.

6. Factors Affecting Weld Quality Tip Distance Ideally should be 1/8 inch to 1/4 inch. As distance increases the rate of heat decreases.

7. Factors Affecting Weld Quality Welding Rod Size Rod size can be used to control bead characteristics. Larger rod can cool the molten pool, increase build-up, and reduce penetration.

8. Characteristics of the Weld The Molten Pool Must stay protected by secondary flame. If contaminated by quickly removing the flame, the pool will be exposed to the atmosphere. If contaminated the pool will spark excessively from rapid burning of the base metal.

9. Characteristics of the Weld Weld Crater Highly susceptible to cracking. Most often caused by the lack of ending weld properly. Can be prevented by moving inner cone away but keeping the secondary flame in position to protect the pool. The pool should also be filled with filler to maintain constant bead height.

10. Joint Welding Beads should be slightly concave with any edges melted back. Take caution to prevent: Cold lap Undercut Porosity Inclusions Joints Butt Lap Tee Edge

11. Joint Welding Tack weld joints to prevent distortion.

12. Video Homework