welding

I am not sure I understand your question. I am reading it as what happens if the ratio between the oxygen and acetylene were not equal.

Equal amounts are required for the hottest possible flame. This is referred to as a neutral flame.

Increasing the percentage of oxygen is called an oxidizing flame. This tends to cause brittle welds with porosity and lower the temperature of the flame.

Increasing the percentage of acetylene is called a carburizing flame. Again the flame temperature is reduced. This flame will add carbon to the weld as well as depositing soot on the surface of the base metal. The soot can interfere with the welding process.

In normal gas welding applications the acetylene regulator should never be adjusted to higher than 15 PSI. Acetylene is unstable. It is mixed with acetone in the cylinder to allow higher pressures with in the cylinder. As the acetylene is drawn off the acetone stays in the cylinder making the acetylene unstable again. Above the recommended safety pressure of 15 PSI the acetylene can cause your torch to explode. There have been cases where faulty or missing check valves with in the torch unit has allowed acetylene to flow into the oxygen regulator during the shut down of a torch. Then the next time the regulators where turned back on to light the torch the higher pressure oxygen compressed the acetylene and resulted in an explosion. Because all things will fail there is a start up and shut down procedure for this type of torch. As this post is quite long I will end here by referring you to the AWS website for the proper safety procedures.