What are the two distinct pressures required to produce a spot weld?

What are the two distinct pressures required to produce a spot weld?

• A. Weld pressure and forge pressure
• B. Clamp pressure and cooling pressure
• C. Preload pressure and exhaust pressure
• D. Torque pressure and hydraulic pressure

Answer: (A)

Spot welding relies on two distinct actions to form a proper weld: generating heat by holding the sheets together with enough electrical contact, and then mechanically forging the molten metal to consolidate the joint. The weld pressure is the clamping force from the electrodes that brings the sheets into intimate contact and provides the current path for resistance heating. This heat turns the faying surfaces into a nugget. After enough heat forms the nugget, a higher, forge (upset) pressure is applied to plastically deform and forge the surrounding metal, expanding and consolidating the nugget, expelling oxide and excess metal (flash), and creating a strong metallurgical bond. These two pressures work in sequence to first create the weld and then shape and strengthen it. Other terms like cooling, torque, or hydraulic concepts don’t describe the essential dual forces used in spot welding.

Spot welding relies on two distinct actions to form a proper weld: generating heat by holding the sheets together with enough electrical contact, and then mechanically forging the molten metal to consolidate the joint. The weld pressure is the clamping force from the electrodes that brings the sheets into intimate contact and provides the current path for resistance heating. This heat turns the faying surfaces into a nugget. After enough heat forms the nugget, a higher, forge (upset) pressure is applied to plastically deform and forge the surrounding metal, expanding and consolidating the nugget, expelling oxide and excess metal (flash), and creating a strong metallurgical bond. These two pressures work in sequence to first create the weld and then shape and strengthen it. Other terms like cooling, torque, or hydraulic concepts don’t describe the essential dual forces used in spot welding.