The technology of gas welding
Gas welding and metal cutting allows you to connect metal structures and components in industry and households. Gas welding is a manufacturing process whereby a combustible gas substance with pure oxygen is used to bind the edges of surfaces at high temperatures. The distance between them is filled with molten material, the source of which is a filler wire.
Gas welding is a fairly simple technology that has many positive aspects:
- Possibility to perform welding works in autonomous mode. No powerful energy source required.
- Availability of simple oversized equipment that can be easily transported.
- The welding process is controlled. Gas torch allows you to vary the operating temperature, speed of heating and angle of the fire.
And also great possibilities of use: the processing is used for joining elements of products made of carbon steel, lead, copper, cast iron, brass, bronze, silumin, aluminum and its alloys.
There are also disadvantages to welding:
- Large heating surface that creates conditions for deformation of neighboring elements.
- The gas welding process is classified as high-risk work. Compressed oxygen, and combustible mixtures require precautions.
- Gas welding is designed for metal thicknesses up to 5 mm.
- No automation of the gas torch.
- High requirements to welder profession.
Advantages and disadvantages
Gas cutting and welding of metals has many advantages, but we are only interested in cutting, which has such pluses:
- In demand when you cut a metal of great thickness or need a cut on the stencil, and the angle grinder can not cope with the curved sections.
- The gas analogue is much more convenient to work with, has a low weight, operates twice as fast as equipment with a gasoline engine.
- Propane costs less than acetylene and gasoline, so its use is more profitable.
- The cutting edge is much narrower and the structure is cleaner than that of an angle grinder or gasoline-powered equipment.
Disadvantages. a narrow range of metals subject to similar treatment.
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Instructions for cutting metal
It is important to connect and prepare the torch properly. Cylinders are connected to tubes with gates at the ends. Next, the gas supply is checked (if it is oxygen-propane metal cutting). the valve on the cylinder is closed, the valve is opened. Then, watching the pressure gauge, slowly open the valve. Pressure must be 0,35-0,55 atm. Then you need to blow out the hose. open the valve. The gas starts to come out with a characteristic sound. If the pressure gauge shows a stable pressure, the valve closes.
The next step is to check the oxygen supply and adjust the pressure. First the valve on the cylinder opens, then the regulator (flow pressure 1.7-2.7 atmospheres). Open oxygen valves on torch to blow out hose. There are two of them: for feeding into the nozzle and for forming the mixture. First you need to open the first one, then the second one (for 3-5 seconds).
Warning! Before turning on the valve, make sure there are no leaks at connections and no children or animals walking around.
The first to open the gas supply valve so that the oxygen, which remained in the mixer after checking it, will come out. Turn the valve until you hear gas coming out. The lighter placed in front of the torch should touch the nozzle. After pushing the spark lever the gas is ignited.
Open the oxygen valve immediately. A change in the color of the flame to blue indicates that the volume is sufficient. oxygen must be added to make the torch grow in size. Gas and oxygen pressure when cutting metal is entirely dependent on the thickness of the workpiece.
Important! If the flame is unstable and sniffles, there is too much oxygen. The volume needs to be reduced so the flame becomes a cone.
The gas cutting technology moves the flame towards the material with the tip, heating up the surface. After the molten metal appears, oxygen begins to flow, igniting it. The jet is increased until the material is cut through. at the same time the nozzle is pushed along the cut line. Sparks and slag are removed by the jet.
Optimal cutting speed is determined by the sparks. they should exit at an angle of 85-90 o. If the angle is smaller, the speed should be reduced. If the workpiece is thick, it must be positioned at an angle to drain the slag. It is not recommended to stop before the process is finished. At the end of the process first shut off the oxygen, then the gas.
The construction of the gas cutter
The structure of the gas cutter is quite simple. The main nodes are:
The barrel, in its turn, consists of an ejector, inlets for hoses, nipples, shutoff and control valves.
All units have similar principles of operation despite their different capacities and other characteristics. Combustible gas and oxygen are fed into the mixing chamber and then flow out through the working nozzle under pressure. Gas flow rate and mixing ratio are regulated by two independent valves at the inlet of the device. This determines the intensity of the flame and its temperature.
The torch, hitting the metal of the workpiece, quickly heats it to melting temperature. Part of the metal evaporates and is carried away with the products of combustion into the atmosphere, part of it oxidizes and turns into slag, and part of it drips. A cut is made in the metal. If you gently guide the torch along the intended line, the heat zone will move and the cut will increase until the desired portion of the workpiece is cut.
As with any other job, even before you start cutting metal with gas, you should prepare the necessary equipment:
- Propane and oxygen cylinder. 1 pc.;
- High-pressure hoses;
- Mouthpiece, which must have certain dimensions.
It is a prerequisite that all cylinders have a reducer, which can be used to adjust the gas supply. Remember that the propane bottle has a reverse thread, so screwing on an additional reducer is not possible.
In general, the gas equipment for metal cutting has a similar device, regardless of the manufacturer. Three valves can be distinguished in the design:
- The first provides the propane supply;
- the second valve allows you to change the oxygen supply;
- the last element is the cutting oxygen valve.
Oxygen valves are usually labeled blue, and propane valves are labeled red or yellow.
metal cutting is performed by the jet of hot flame acting on the metal, which is created with the torch. When it is turned on, propane and oxygen mix in a special mixing chamber, which creates a combustible mixture.
With the propane torch you can cut metal up to 300 mm thick. Detailed installation is complete with elements, which are mostly replaceable. For this reason, if a part fails, the operator has no difficulty in repairing it on the spot.
Great care must be taken when selecting the nozzle. A key parameter to watch is the thickness of the metal. If you have to deal with the object, which involves elements of different thickness, ranging from 6 to 300 mm, it is necessary to prepare the mouthpieces, having internal numbers from 1 to 2, and external. from 1 to 5.
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Drawbacks of machining
Low-carbon steel is best suited for gas cutting, but medium- and high-carbon steel are not really the right material for cutting. High carbon content increases the ignition temperature and lowers the melting temperature. And that condition makes it difficult to cut.
It is difficult to cut metal with a gas mixture if it has a low thermal conductivity. Therefore these types of material are not suitable for machining.
Gas cutting of metal should be performed only by a qualified and experienced specialist. It is important to observe all the key factors for proper processing: oxygen pressure and speed of the procedure. It is necessary to take into account the thickness of the product and the diameter of the nozzle of the cutting torch. If the speed of oxidation and metal cutting do not match each other, you will get poor quality processing.
Oxygen cutting involves use of explosive substances. If safety rules are not followed, there is a high probability of an explosion of the gas-air mixture, it is necessary to monitor the condition of the gas equipment. To protect against burns you need to use personal protective equipment.
Significant disadvantage is the possibility of metal deformation and poor cutting accuracy.
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Basic equipment for gas cutting is a torch. Welding and fusion nozzle included.
Thanks to the torch you can control the dosage of gas mixture and oxygen. Also with the help of this equipment is carried out ignition of the combustible mixture, the supply of flame to the place of treatment.
The cutter consists of two units: a cutting unit and a heating unit. The first is represented by an oxygen outlet tube, a valve and an internal type nozzle.
The heating block includes valves for pressure adjustment of the gas mixture and oxygen. There is also a feeding tube, an external view nozzle, a mixing chamber and an injector cell.
Torches can be handheld or machine torches. The latter are stationary, so it is preferable to use manual torches for repair work.
In addition, the following gas cutting equipment is used:
- Pressure reducer. designed to reduce pressure;
- device for changing the pressure;
- A steel cylinder with gas and oxygen;
- connecting hoses.
Before using equipment it is important to check its operability to avoid the risk of explosion of the cylinder or pressure reducer. The torch is pre-blown with oxygen.
The gas cutter with his own hands
Here is a variant of a compact and simple, but quite effective gas cutter. It easily melts and cuts copper wires and heats sheet metal in a short time (seconds). On this example you can understand the principle of building a more powerful self-made gadget and, if you have a keen desire, create it. To make it you will need:
- two large medical droppers;
- A needle to inflate balls (volleyballs/footballs);
- aquarium compressor. Plastic two-liter bottle can be substituted;
- Cylinder for filling gas lighters with propane;
- copper wire;
- complete (stand with tubs, solder, flux, etc. п.) soldering iron;
- Heat-gun (thermal glue);
- a removable nipple for a car camera;
- ) a fine file or fine-grained emery stone.
The principle of operation of the machine, after reading the article, is intuitively clear from the figure.
The gas cutter with his own hands. East. http://www.lifetweaks.ru/dlya-avtolyubitelya/gazovyj-mini-rezak-svoimi-rukami/.
In a large needle we make a hole (notch) and pass through it bent medical (its sharp end we sharpen). We wrap the copper wire and solder it for sealing (it reminds us of a gas torch?). It remains to ensure the flow of air from the compressor and propane from the cylinder. Restrictor clips on the drip tubes will adjust the torch flame. The rest we suggest you to think over independently and you will receive a gas cutter with your own hands.
Where to buy
For purchasing we advise to visit this section of the online store “All Tools”.
A regular customer of Trading House “DOCA”, The experienced gas cutter decided to share with us how to choose a gas cutter. Please note that the opinion expressed in the article is slightly different from that of our experts on the subject. We’ll make our own recommendations in a future article.
So, how to choose the right gas torch.
To begin with, it should be clear that any purchase entails inevitable costs. If you are ready to buy for each specific task a highly specialized gas cutter, then the following text will not be of interest to you.
Any manufacturer (including the gas-welding equipment). salesman in its essence. It’s important for both (the manufacturer) and the other (the salesman) to sell their product, and sell as much as possible in quantitative terms.
Before you start searching for the cutter it is necessary to understand that in spite of variety of combustible gases (propane, acetylene) and mixtures (gasoline, kerosene) you and all other planet inhabitants in 99 cases from 100 will have to deal with propane torches, purely for economy reasons. You will cut a black metal (steel) mainly 3-4 mm thick, sometimes 10-20 mm is possible. With such thickness, however, as well as 300 mm, yes even 800 mm, any propane torch will cope. For cutting thicker metal you will need to increase the working pressure and put on a torch the inner and outer nozzles of a larger size.
I’d love to see a video from the above-mentioned respected manufacturers of gas-welding equipment, which will also clearly explain the 10 differences between the cutters P1 and P3.
Since, this roller will never appear, with your permission I will do it. So: the difference between torches P1 and P3 of any manufacturer is a thickness of the cut metal by definition and a complete set of the last (P3) by the internal nozzles of the big sizes. Work experience as a gas cutter gives the right to declare: with the torch P1 you can freely cut metal of any freely accessible thickness.
Direct choice of gas cutter
Think about the length of the torch. Experience has shown that the standard length of 485 mm in practice means 25 centimeters from the hand holding the torch to the tip of the flame. On clean sheet metal these numbers won’t tell you anything, but on painted, oily surfaces you’ll soon wish you’d taken an extended gas torch (768-800mm).
When looking at the length, don’t forget that it’s from the mouthpiece to the tip of the nozzle, and that’s minus almost 10 centimeters.