Fig. 23.—More Oxygen Pressure Applied. Flame Contains Slight Excess of Acetylene, and is Known as “Carbonizing.”
Fig. 24.—“Neutral” Flame. Correct Proportions of Oxygen and Acetylene Gases.
Fig. 25.—“Oxidizing” Flame. Too much Oxygen Present.
(33) As soon as an operator has gas pressure in his regulators, he begins wondering how much pressure should be placed on his line, that is, the portion between the regulator and the torch. Of course, this depends upon the size of the tip, but the operator should have some means of approximating this pressure without going to his manufacturer’s chart every time. A neutral flame, that is, theoretically equal parts of oxygen and acetylene, is desired for welding. Now in lighting, the flame should stand away from the tip a slight distance, in torches other than the low-pressure type, while in these there will only be a good full flame issue from the tip. Enough oxygen must be in evidence to bring this acetylene flame down to the neutral point. If not enough pressure is used, this result cannot be obtained, and of course, more pressure must be introduced. It is better to have too much pressure than not enough on the line, for the operator may use his torch valve to again regulate this pressure and is always sure of enough gas. Theoretically, all adjustments should be made at the regulator, but in practice this is very seldom carried out. The accompanying cuts will illustrate the five conditions which every welder should be familiar with, in the flame adjustment. [Fig. 21] shows the acetylene turned on full; no oxygen has as yet been introduced. The flame has a yellow appearance and is very rich in carbon, as can be seen by the soot given off. In [Fig. 22] we see the oxygen being turned on; the yellow flame (A) is gradually giving way to a white part at (B). In this condition we say that a feather flame exists. [Fig. 23] shows slightly more oxygen pressure. In [Fig. 24] we have the neutral flame, which can be readily recognized on account of its bluish white color and well-defined outline, appearing like the end of an unused piece of chalk, only, of course, much smaller. In [Fig. 25] can be seen an excess or too much pressure of oxygen. It will be noticed that the neutral flame assumes a more bluish color, is a little pointed, and a very noticeable hissing sound is in evidence. This is what is called an oxidizing flame and will be again referred to. Too much oxygen is used. Operators who attempt to turn on the oxygen first and then light it, will find that it does not burn, and their efforts will be useless. In picking up a torch for the first time, any operator can turn on one valve and detect by the odor of the gas, whether it is oxygen or the fuel gas, and can light it in accordance. Some operators, however, attempt to turn on a little of each gas and light. This is not to be recommended, for flashbacks may occur. When the welder accustoms himself to turning on enough pressure to accommodate whatever sized tip he may have, he will find that there is no great need for paying attention to the pressure gauges on his regulators except to check up on the full drums of oxygen, and to tell whether he has enough gas left to complete a certain piece of work.
(34) A neutral flame is theoretically composed of equal parts of oxygen and acetylene ignited, but this ratio is very seldom worked out in practice. There is usually an excess of oxygen in evidence. A neutral flame is generally spoken of as being over 6000 degrees Fahrenheit, and this does not vary with the different sized tips as most welders think. Of course there are different quantities of heat between a very small tip and a large sized one, but the temperature of the flame is the same.
(35) If too much acetylene gas is used, a feather flame such as was seen in [Fig. 23] will appear. This has a carbonizing effect on the weld, for it introduces carbon and causes the weld to become very brittle.
(36) If too much oxygen gas is used, the effect shown in [Fig. 25] will take place, and the weld will have oxygen introduced, which is a very detrimental feature, and is particularly noticeable in working on steel, for it raises a white foam over the surface of the melted metal, which sometimes is worked right into the weld itself. An experienced welder will always know just what kind of a flame action he is obtaining on his weld, not because he takes the flame away every time he wishes to look at it, but he can tell by the action of his metal exactly the nature of his flame.