The correct use of gas cutting gas welding, the welding method of gas welding

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The welding methods of gas welding are:1. When igniting the flame, first open the oxygen valve to release a trace amount of oxygen, 2. Unscrew the acetylene valve to release a small amount of acetylene, close the welding nozzle to the fire source, and ignite the mixed gas, 3. Then adjust the gas ratio to obtain the required gas according to the need.

4. After the flame ignition is adjusted, hold the welding torch in the right hand and the welding wire in the left hand, and weld left or right as needed.

Left-facing welding is suitable for thin steel plates and non-ferrous metals, and right-facing is suitable for welding thicker weldments. At the end of welding and when stopping in the middle of the process, close the acetylene valve first and then the oxygen valve.

When gas welding, it is necessary to pay attention to the normal welding process, first of all, the weldment butt, this step is quite important, the weld with poor buttling, the next will have too much impact on the welding work. Then, weld treatment, welding, weld beautification, acceptance. Different welding methods have different details, like electric welding, gas welding, gas shielded welding, brazing, etc.

Welding methods of gas welding:

1. Clean up before welding.

Before gas welding, the groove of the workpiece and its two sides and the surface of the welding wire must be cleaned of oil, oxide and other dirt. Oiling can be cleaned with solvents such as gasoline, acetone, kerosene, etc., or baked with flames; Oxide removal can be cleaned by mechanical methods such as sandpaper, wire brush, file, scraper, angle grinder, etc., and oxides on the metal surface can also be dissolved with acid or alkali. After cleaning, rinse with clean water and dry with a flame.

2. Hold the torch. Generally, the right hand holds the welding torch, the left hand holds the welding wire, the right thumb is located at the acetylene switch, the index finger is located at the oxygen switch, which is convenient to adjust the flow of gas at any time, and the other three fingers hold the torch handle, which is convenient for the welding nozzle to swing, adjust the heat input into the molten pool, change the position of the welding, and change the angle between the welding nozzle and the weldment.

3. Positioning welding.

When welding, the weldment should first be positioned welded. If the weldment is a thin plate, it can be welded from the middle to both ends, and the length of the positioning weld is generally 5 7mm, and the interval is 50 100mm; If the weldment is thick (plate thickness > 4mm), the positioning welding can start from both ends and weld to the middle, the length of the positioning welding seam is 20 30mm, and the interval is 200 300mm.

4. Preheating. At the beginning of welding, the weldment is preheated due to the low temperature of the weldment. In order to shorten the heating time and form a molten pool as soon as possible, the center of the flame (the center of the torch nozzle) can be perpendicular to the workpiece and the flame can move back and forth to ensure that the welding place is heated evenly.

5. Welding. After the heating is completed, the center of the flame is tilted, and when the molten droplets of the welding wire fill the molten pool, the flame and the welding wire can be moved for continuous welding. During the welding process, the flame inclination angle can be selected between 20° and 60° depending on the thickness of the weldment.

The welding material is different, the inclination angle of the welding nozzle is different, such as when welding copper, the inclination angle of the welding nozzle is 80 °; When welding aluminum, the inclination angle of the welding nozzle is 10°.

6. a joint. When welding is resumed after a pause, the original weld pool and the weld close to the weld pool are remelted with a flame, and a new weld pool is formed before the wire is fed. When welding important workpieces, each re-welding should overlap 8 10mm with the previous weld to ensure that the high-quality joint is obtained.

7. Wrap up. When the welding is finished, the final arc pit is filled in order for the weld to be well formed. At this time, the angle of inclination in the center of the flame should be reduced, and the flame should be swung to prevent the weldment from burning out, and at the same time, the welding speed should be increased and some more welding wire should be added until the arc pit is filled.

In order to prevent oxygen and nitrogen from entering the molten pool, an external flame can be used to protect the molten pool for a certain period of time, and then move away after seeing that the surface is no longer red.

8. Post-welding treatment.

The flux and welding slag remaining in and near the weld after welding should be cleaned in time, otherwise the weldment will be corroded. The method of cleaning is to first scrub the welded joint with a hard brush in 60 80 hot water, and then put it into 60 80 and soak it in an aqueous solution of chromium anhydride with a mass fraction of 2% 3% for 5 10min after washing the important components, and then carefully scrub with a stiff brush, and finally rinse it with hot water.

The steps of gas welding are:

1. Pre-welding inspection: It is necessary to check whether the injection and suction performance is normal, and whether there is air leakage at the connecting parts of the welding torch and the needle valve of the adjusting handwheel. Gas welding must be done with a gas welding gun, and pay attention to safety before use.

2. Ignition: When ignition, you can open the acetylene handwheel first, ignite the acetylene and immediately open the oxygen regulating valve handwheel to adjust the flame, or you can open the oxygen adjustment handwheel slightly when ignition, and then open the acetylene adjustment handwheel and ignite immediately.

3. Preheating adjustment: After ignition, preheat for a period of time to slowly increase the oxygen concentration, and the flame will change from long to short, forming a neutral flame.

4. Welding: find the welding point, weld, cut and other operations on the object. Wear a protective shield to protect your eyes.

If flashback occurs during operation, turn off the oxygen regulating handwheel and then turn off the acetylene regulating handwheel in an emergency. After the tempering is extinguished, the welding nozzle is placed in water to cool, and then the oxygen is turned on to blow out the soot in the torch, and then the fire is re-ignited.

5. Flame-out: When the flame is out of use, the acetylene adjustment handwheel should be closed first to prevent backfire, and then the oxygen valve should be closed.

6. Post-welding cleaning: the welding torch should be hung in an appropriate place, or the hose should be removed and the torch should be stored in the toolbox.

Steps:

Gas welding ignition

For ignition, the oxygen valve of the torch is adjusted to a small oxygen flow rate, and then the acetylene gas is slowly turned on.

valve, ignite, and then adjust the flow of oxygen and acetylene gas until the flame is adjusted to the desired size, and the welding operation can be carried out.

The method of regulating the flame

According to the different mixing ratio of oxygen and acetylene, gas welding flame can be divided into: oxidation flame, neutral flame, and carbonization flame. The size of the flame during welding can be controlled and adjusted by adjusting the oxygen valve and acetylene gas valve to obtain an oxidizing flame, a neutral flame or a carbonization flame.

Adjustment method of neutral flame: after igniting the torch, gradually increase the oxygen flow, the flame changes from long to short, the color changes from light red to blue and white, when the contour of the flame core, inner flame and outer flame is quite clear, it is the standard neutral flame.

Adjustment method of carbonization flame: on the basis of neutral flame, increase the flow rate of acetylene gas, or reduce the flow rate of oxygen, so that the flame changes from short to long, and the color changes from blue-white to orange-yellow, the carbonization flame can be obtained.

Oxidation flame adjustment method: on the basis of the neutral flame, gradually increase the flow of oxygen, so that the length of the flame becomes shorter, straighter, and emitting a "hissing" sound to obtain the oxidation flame.

Carry out welding

Before ignition, it is necessary to check whether the injection and suction performance is normal, and whether there is air leakage at the connecting parts of the welding torch and the needle valve of the adjusting handwheel.

Gas welding flameout

When extinguishing the flame, the acetylene gas valve should be closed first, and then the oxygen valve.

There are 4 steps in the gas welding operation:

1. Ignition: Open the acetylene valve first, ignite the acetylene and open the oxygen regulating valve immediately.

2. Adjust the flame: The flame that starts to ignite is the carbonization flame, and then gradually opens the large oxygen valve to adjust it to a neutral flame.

3. Carry out welding.

4. Flameout: When the workpiece is extinguished after welding, the acetylene valve should be closed first and then the oxygen valve should be closed to avoid tempering and reduce smoke and dust.

If it is found that the acetylene and oxygen pressure or flow rate changes during the operation, and cannot meet the work requirements and needs to be adjusted, the welding must be stopped, the flame must be extinguished, and the ignition must be re-ignited after treatment. It is forbidden to adjust the treatment with flame to prevent backfire caused by fluctuations in generator pressure and flow.

Preparation. Check the use of the equipment and whether the surrounding environment is safe;

removal of dirt, etc.;

Stake out according to the drawing;

Raise and stabilize the cut piece;

Check the injection and suction performance of the cutting torch;

Check whether the wind line is good;

Adjust the energy rate of the preheating flame.

and nature; After the above preparations are completed, the trial cutting will be carried out.

Operational techniques. The operation of gas cutting is divided into four steps: ignition, cutting, normal gas cutting, and stop cutting.

Ignition: Before ignition, turn on the acetylene, then slightly open the oxygen valve, and use an ignition gun.

or match lighting. Under normal circumstances, a special lighter should be used for ignition. In the absence of a musket, a match can also be used to ignite the fire, but attention must be paid to the safety of the operator and not to be burned by the ejected flame.

At the beginning of the carbonization flame, the oxygen flow should be gradually increased, and the flame should be adjusted to a neutral flame or a flame with slightly oxidizing properties.

Cutting: The cutting point should be selected at the edge of the cutting piece, first heat the metal with a preheating flame, and when the preheating is bright red, move the flame to the edge, and slowly open the cutting oxygen valve, with the increase of oxygen flow, bright red iron slag will fly out from the back of the cutting piece, proving that the workpiece has been cut through, and the cutting torch can start to move from right to left at an appropriate speed according to the thickness of the workpiece.

Normal gas cuttingAfter cutting, the moving speed of the torch should be uniform, and the distance between the cutting nozzle and the cutting piece should be about equal to the length of the flame core 2 4mm. The nozzle can be tilted 20° to 30° backward (i.e. in the direction of the cutting forward).

In the process of gas cutting, if there is a detonation and backfire, the cutting oxygen valve should be closed immediately, and then the preheating oxygen valve and acetylene valve should be closed in turn to suspend the gas cutting process. Remove dirt from the passage with a through-needle. After the treatment is normal, re-gas cutting.

Stop cuttingAt the end of the day, the torch should be tilted at an angle in the opposite direction of the gas cutting, so that the lower part of the steel plate can be cut through in advance, so that the cut looks neat at the end. Finally, the oxygen valve and acetylene valve are closed, and the whole gas cutting process is completed.

When the thickness of the steel plate is more than 25mm, a large torch and nozzle should be used, and the preheating flame and cutting oxygen flow should be increased. In the gas cutting process, the cutting speed should be slow, and the transverse crescent shape oscillation should be done appropriately to widen the incision and allow for slag discharge.

Gas cutting refers to the use of gas flame to preheat the cut metal to the ignition point, so that it burns violently in the pure oxygen flow, forming slag and releasing a large amount of heat, under the blowing force of high-pressure oxygen, the oxidized slag is blown off: the heat released further preheats the next layer of metal to make it reach the melting point. The gas cutting process of metal is a continuous process of preheating, combustion, and slag blowing, which is essentially the process of metal combustion in pure oxygen, rather than the melting process.

1. Put the guide rail, put the cutting machine on the guide rail, the two ends of the guide rail should be aligned, when cutting the circle, adjust the height of the cutting nozzle, the distance and angle relative to the trolley, so as to ensure continuous cutting in the area of the plate, 2. Connect the gas pipe, distinguish the oxygen pipe and the gas pipe.

3. Open the oxygen control valve and gas control valve, and confirm the gas cylinder pressure and output air pressure to ensure that the gas supply is sufficient and saving.

4 ignition; Turn on the gas and preheat oxygen, use a lighter to light the fire from the side.

5. Start cutting; , use the preheating flame to heat the start point (at this time the high-pressure oxygen valve is closed), the preheating time should depend on the temperature of the metal, generally heated to the surface of the workpiece close to melting (the surface is orange-red). At this time, gently open the high-pressure oxygen valve and start gas cutting. If the preheating place can not be cut, it means that the preheating temperature is too low, the high-pressure oxygen should be turned off to continue preheating, the front end of the flame core of the preheating flame should be 2 4mm away from the surface of the workpiece, and at the same time, it should be noted that there should be a certain angle between the torch and the workpiece, when the workpiece with a thickness of 5 30mm is cut by gas, the cutting torch should be perpendicular to the workpiece; When the thickness is less than 5mm, the torch can be tilted back 5 10°; If the thickness exceeds 30mm, the torch can be tilted forward by 5 10° at the beginning of gas cutting, and when it is cut through, the cutting torch can be perpendicular to the workpiece until the gas cutting is completed.

If the preheated area is cut off, continue to increase the amount of high-pressure oxygen to increase the depth of the incision until it is completely cut through.

6.When gas cutting steel of different thicknesses, the selection of the cutting nozzle and the adjustment of oxygen working pressure are closely related to the quality and efficiency of gas cutting. For example, if you use a cutting nozzle that is too small to cut thick steel, the cutting work will not be able to go smoothly because you do not have sufficient oxygen combustion and injection capacity, and even if you barely cut it again and again, the quality will be poor and the efficiency will be low.

On the contrary, if you use a large nozzle to cut thin steel, not only will a lot of oxygen and acetylene be wasted, but the quality of the gas cutting will not be good. Therefore, it is necessary to choose the size of the cutting nozzle. Relation of the pressure of cutting oxygen to the thickness of the metal:

Insufficient pressure, not only the cutting speed is slow, but also the slag is not easy to blow off, the incision is uneven, and sometimes even the cutting can not be penetrated; When the pressure is excessive, in addition to the increased oxygen consumption, the metal is also prone to cooling, resulting in a lower cutting speed, wider cuts, and rough surfaces.

1. First of all, use the oxygen pressure reducer and acetylene pressure reducer to correctly connect with the oxygen and acetylene cylinders, and adjust them to the working pressure respectively, and then carry out cutting and welding work. Both the grip of the gas cutting gun and the gas welding gun have instructions for connecting oxygen and acetylene gas.

2. When ignition, open the oxygen valve first, then open the acetylene valve and ignite it immediately, and the opposite is true when the flame is turned off. In case of tempering, acetylene gas should be turned off immediately.

3. Oxygen cylinders and acetylene cylinders should be placed standing and kept at a distance of more than 5 meters from the operation area.

4. Install oxygen meter and acetylene meter: When installing the meter, adjust the pressure adjustment valve to a place without top pressure.

5. The basic operation methods include the ignition, adjustment and extinguishing of the oxy-acetylene flame, the movement of the welding torch and welding wire during the welding process, the joint and the operation of the finish.