In welding one needs to melt base metals to fuse m.

There are three basic flame types: neutral (balanced), excess acetylene (carburizing), and excess oxygen (oxidizing) as shown below.

The strength of perfectly welded joint is more than parent metal, due to formation of alloy. The alloy formation at welded portion makes it strongest portion while nearby zones where uncontrolled cooling take place because of heat is weakest zone (heat affected zone). In general we can say that on basis of strength: welded portion > parent material > heat affected zone.

Torch mixes fuel and oxygen and controls delivery. It has two control valves, one for controlling flow of acetylene and or of oxygen, entering a chamber called mixing chamber where two gases are mixed in a correct proportion.

Flux is used to completely cover welded zone. It prevents oxidation of weld joint and spattering of molten metal.

Maximum material limit of hole is smallest diameter of hole. Minimum material limit of hole is largest diameter of hole.

In order to prevent oxidation and retain molten metal in stud welding ceramic rings are used.

In neutral flame oxygen is in same proportion with acetylene. Neutral welding flames are commonly used to weld: mild steel, stainless steel, cast iron, copper, aluminium, etc.

In homogenous joining process filler material used is same as parent material.

The chemical formula of acetylene is C₂H₂. 1 mole of acetylene can produce KJ/mol of heat.