McG 4340 - Mechanical Engineering - Welding and Cutting Processes

Faculty of Engineering

Department of Mechanical Engineering

Mechanical Engineering Lab

MCG 4340

Lab Report for Welding and Cutting Processes

Professor:  Stavros Tavoularis

1. The welding processes that were conducted under supervision are:

• Stick electrode welding
• MIG
• TIG
• Spot welding
• Oxy-Acetylene cutting
• Plasma Cutting

1. General Information

      The following are the processes that were attempted in the lab:

• Stick welding (SMAW): the welder follows a manual process of stick welding. An electric current flows through the stick to form an arc between the stick and the metal to join them. It is often used in steel structures and industrial welding processes.
• MIG: It stands for metal inert gas welding. It uses a shielding gas along the wire electrode. It heats up the two metals when joined. This requires constant voltage and direct current power source. MIG welding is the most common industrial welding process.
• TIG: this welding process is gas tungsten arc welding. It is commonly used to weld thick sections of stainless steel. It is a process that uses a tungsten electrode.
• Spot welding: it is a process in which contacting metal surfaces are joined by heat obtained from resistance to electric current. Pieces are held together under pressure from the electrodes. It is a fairly quick process with many applications for simple parts.
• Oxy-Acetylene Cutting: It consists of mixing oxygen and acetylene gas to create a flame capable of melting steel. It is mostly used for maintenance work and gas metal cutting. It is also common for brazing softer metals like copper and solder metal. It can also be used for fragile materials such as refrigeration piping.
• Plasma cutting: It works by sending an electric arc through a gas that is passing through a constricted opening. The temperature of the gas is elevated to the point where it enters a plasma state. The plasma cuts through electrically conducted material.
• Safety measures: safety is extremely crucial in this experiment especially due to the fact that we are dealing with hot surfaces and sparks. It is essential to follow the safety rules and the MCG 4340 course manual in regards to proper conduct in the lab.

1. Questions

1. Which welding process would you used to build a stainless steel 20 ga aircraft muffler? Why?

When welding thin metal, the main objective is to avoid warping, burn-through and excessive heat affected zones while still ensuring the weld has sufficient mechanical strength for the application. The welding process that is most suitable for this application is short circuit transfer MIG ("short arc"). For making an aircraft muffler, welding stainless steel metal often means a constant battle between efficiency vs. burn-through, warping, excessive heat affected zones (HAZ) and weld appearance.