Question

name olivia bettis date 8/15/25 class welding 5th instructor instructors initials lesson grade lesson 3a the physics of welding objectives: you will be able to explain the effects of heat, pressure, expansion, and contraction on welding. you will understand and be able to describe the chemical and mechanical properties of metal. instructions: read chapter 3 up to the heat treating section and study figures 3 - 1 through 3 - 6. then, answer or complete the following questions. 1. when two metals are melted and flow together, they are said to be welded or ________ together. 2. in which direction, a or b, will the vertical piece tend to move when the following joint is welded? a ← b → 3. which of the following can be used to relieve stress and prevent movement during welding? a. tack welding. b. align the parts to allow for contraction during welding. c. preheating the parts. d. all of the above. 4. ______ is a welding process in which very clean pieces of metal are fused together under considerable pressure, without an outside heat source or filler metal. 5. what term describes a materials ability to resist pulling forces? ______ 6. explain how the resistance spot welding process uses both heat and pressure to form a weld. 7. the properties of a metal are largely determined by its ______ composition (the elements that make up the metal). 8. as a metal is cooled, it will always try to ________. a. expand b. crack c. contract d. lose toughness

Explanation:

Step1: Recall welding terminology

When two metals are melted and flow together, they are welded or fused together.

Step2: Analyze joint - movement in welding

When welding the given joint, due to heat - induced expansion and contraction, the vertical piece will tend to move towards the side with more heat input. Assuming the heat source is on the right, it will move towards B.

Step3: Evaluate stress - relief methods

Tack welding helps hold parts in place, aligning parts allows for proper contraction, and preheating reduces thermal shock. So all of the above (A, B, C) can be used to relieve stress and prevent movement during welding.

Step4: Identify welding process

The welding process where very clean pieces of metal are fused together under considerable pressure without an outside heat source or filler metal is called cold welding.

Step5: Define material property term

The term that describes a material's ability to resist pulling forces is tensile strength.

Step6: Explain resistance spot welding

Resistance spot welding passes an electric current through the metal pieces at the contact point. The resistance of the metal to the current generates heat, and external pressure is applied simultaneously to fuse the metals together at the spot.

Step7: Understand metal properties

The properties of a metal are largely determined by its chemical composition (the elements that make up the metal).

Step8: Analyze metal behavior on cooling

As a metal is cooled, it always tries to contract.

Answer:

1. fused
2. B
3. D. All of the above
4. cold welding
5. tensile strength
6. Resistance spot welding passes an electric current through the metal pieces at the contact point. The resistance of the metal to the current generates heat, and external pressure is applied simultaneously to fuse the metals together at the spot.
7. chemical
8. C. contract