Welding personnel must have certain flame cutting skills in addition to basic welding, mainly manual flame cutting skills, which are used to assemble and size or repair workpieces.
The oxyfuel cutting process goes through three processes of preheating, burning and blowing slag, and its essence is the process of burning metal in pure oxygen, not the process of melting.
Flame cutting is mainly used for processing low carbon and low alloy steel. However, cast iron, high-chromium steel, chromium-nickel steel, copper, aluminum and their alloys do not cut with oxygen, so they can be cut with plasma.
Knowing the principle and basic knowledge of flame cutting does not mean you can practice it. It is not easy to work with gas cutting by hand. There are two main reasons for this:
1. Gas cutting includes open flame operations. Oxygen and acetylene cylinders present an explosion hazard. Although most torches on the market now have tempering protection features, conventional torches still exist and are used in large quantities in some special cases, and there are certain hidden tempering hazards. Fortunately, there are certain dangers and certain psychological burdens.
2.The flame cutting theory is boring, and the actual operation needs to adjust the flame. The oxygen bottle and acetylene bottle tools and the three handles on the cutter need to be refined. The actual operation needs a certain amount of time and accumulation.
The flame cutting operation may vary depending on personal habits.1. Adjust the position of the gas cylinder and adjust the oxygen and acetylene pressure values
When performing gas cutting and hot work, the acetylene cylinder and the oxygen cylinder must be placed vertically, and the distance between them must be at least 5 m, and the distance between them and the place of hot work must not be less than 10 m, and they must not must be exposed to the hot sun. Then adjust the oxygen and acetylene pressure values. Generally speaking, the larger the cutting nozzle and the thicker the workpiece, the higher the required pressure.
Generally, oxygen pressure gauge adjustment range: 0.2-0.5MPa, acetylene pressure adjustment range: 0.05-0.1MPa.2. Change your posture
Generally, the right hand holds the handle of the torch, and the thumb and forefinger of the right hand holds the preheat oxygen valve, which is convenient for adjusting the preheat flame and timely turning off the preheat oxygen during vacation.
The thumb and forefinger of the left hand hold the switch that turns off the oxygen valve, and at the same time, they also play a role in sensing the direction. The remaining three fingers firmly held the pistol grip. Do not tilt the upper body too low and watch the mouth of the incision and the secant lline before incision. Usually cut from right to left.3. Switch off the ignition
When starting cutting, call out the neutral preheat flame first, and preheat the edge of the steel sheet until it is heated to a temperature where it can burn in oxygen, that is, when the surface layer of the cutting element is about to melt, the notch When the position becomes reddish, partially move the flame beyond the edge line and at the same time slowly open the cutting oxygen valve.
[Neutral preheat flame standard: after ignition, hold the acetylene knob still and slowly turn the oxygen preheat knob. A bright yellow spot forms at the cutting tip, and a thin blue flame, about 15 cm long, forms at the front end. This is a standard neutral preheat flame, and the adjustment was successful]
When the iron oxide slag flies out along with the flow of oxygen, it proves that it has been cut. At this time, move the cutter to gradually cut forward. When cutting along the outer contour of the curve, the cutting nozzle must be strictly perpendicular to the surface of the cutting metal, and the cutting nozzle must be in a vertical position with the metal surface being cut; the nozzle is at an angle of 10°~30° to the opposite cutting direction to better heat the edge of the cut piece and facilitate the start of the cutting process.
During flame cutting, if the operator needs to change the position of the body, the cutting oxygen valve should be closed first, and then the body position should be changed. When cutting a thinner steel plate, when the cutting oxygen is turned off, the flame must quickly leave the surface of the steel plate to prevent the thin plate from rapidly heating up, causing the kerf to deform and rejoin.
When cutting continues, the cutting nozzle should be directed to the cutting seam and properly preheated, and then slowly open the cutting oxygen valve to continue cutting. When the cutting is nearing the end, the cutting nozzle should be tilted in the direction opposite to the cutting direction to facilitate the pre-cutting of the bottom of the steel plate, so that the cutting seam at the end is more accurate.4. Turn off the fire
When the end point is reached, quickly close the cutting oxygen valve and raise the torch, then close the acetylene valve, and finally close the preheat oxygen valve.
The above is the basic flame cutting process. As a rule, you need to observe the basic movements of the master, and after familiarizing yourself with the process, practice on a thin plate several times before you can start working. Hand held flame cutting is a basic ability of welding personnel that needs to be understood and mastered.