Manual gas cutting of metal. The necessary equipment

You need the services of a gas cutter? We can help you!

Cutting metal, as well as the manufacture of metal parts and structures can be performed by different methods of cutting metal: with gas, plasma and abrasive. Oxygen gas cutting is the most common process for cutting and cutting metal. It can be performed in almost all positions, including the vertical plane. Oxygen cutting consists of several stages:

M-Welding Company performs dismantling of various metal constructions, including oversized, high-altitude works. We offer gas cutting services in any area of Moscow and the Moscow region, for this you only need to leave an application online or by phone by calling the number listed here. We guarantee the most prompt departure and high quality gas metal cutting services.

Skill of our certified gas cutters is beyond doubt. They are familiar with all the subtleties of metal cutting: they can correctly set the pressure of cutting oxygen, which determines the speed and quality of cutting, control its level, can sense and find the most favorable mode, maintaining it throughout the cutting process, intelligently set the torch flame. In our work we use additional devices: guiding rulers, supporting carts, compasses.

Professional crews of experienced gas cutters. we are always ready to help.

The business made by our hands cannot be boring, especially if it is aimed at providing quality services to our customers.

Features of application

To understand how to properly cut metal with a torch, it is necessary to study the design and know that such equipment is not used for cutting steels with high m. к. It is not possible to create a temperature that can sustainably melt. When cutting cast iron workpieces or structures, there is a concentration of graphite between the grains of metal, which makes it difficult to work.

Can not be used to cut products made of aluminum, copper and alloys based on it.

Gas cutting technology of metal

By the technology of gas cutting, we mean a set of sequential actions, which include:

Preparing the metal surface for cutting.

Before you start the cutting process, you must clean the surface of the metal to be cut. You need to remove scale, rust and other contaminations. Use a wire brush to deburr the surface. The cleaning width of the area to be cut is approximately 30-50 mm.

Torch ignition sequence.

All taps on torch must be closed. First you need to open the valve with oxygen. Next, you need to open the valve of combustible gas. Approach with lit flame at a distance from mouthpiece. Be careful. At the time of ignition, the torch flame is already oxygenated and will immediately have a high temperature. Keep your fingers safe. Adjust flame with two torch valves.

First use the torch flame to warm up the surface of the metal to be cut. Heat up until the surface layer of metal is molten. Hold the torch vertically with respect to the metal surface. If the metal is very thick (over 50 mm), the nozzle of the torch can be directed at an angle of 10-15º relative to the metal. This will improve the heating of the metal.

Distance from nozzle to metal.

For quality cutting, it is primarily necessary that the core of the flame was at a distance of 2-3 mm from the metal surface. During the cutting process it is recommended to maintain this distance during the whole process. For rectilinear cuts it is possible to use additional carts attached to the cutter. To cut plate with a thickness of more than 80 mm the distance from the nozzle to the metal should be doubled.

Cutting position.

When cutting metal with thickness up to 50 mm the torch should be held at a 20-30º angle to the opposite side of the motion.

Maintaining optimum cutting speed is very important. Cutting at low cutting speeds causes intensive melting of the cut metal edges. High speed will cause incomplete penetration of the metal surface.

The table below will be approximate speed of cutting slalie in mm / min:

Thickness of steel to be cut in mm

How to cut metal with an oxypropane torch

Metal cutting is necessary for dismantling metal structures, cutting of any kind of rolled products before machining or welding. And if a sheet or section of small thickness can be cut with a mechanical tool (manual, electric or hydraulic). To work with metal blanks of great thickness you need a gas cutter, or in professional slang. autogenous. In this article, the master plumber will tell you how to cut metal with an oxypropane torch.

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Regardless of the size of the auto-gen and the type of heating gas mixture, cutting is performed due to metal combustion in a jet of pure oxygen pumped through the nozzle of the head into the working area.

Note! The basic and fundamental condition of gas cutting is that the burning temperature must be lower than the melting temperature. Otherwise, the metal, before it starts to burn, will melt and flow. Low-carbon steels correspond to this condition, but non-ferrous metals and cast iron do not

Most alloyed steels are also not amenable to gas cutting. there are restrictions on the maximum allowable doses of alloying elements, carbon and impurities, above which the burning of metal in oxygen becomes unstable or even interrupts.The cutting process itself can be broken down into two phases:

  • Heating of a confined area of the part to a temperature at which the metal starts to burn. And in order to obtain a plume of heating flame, some of the process oxygen is mixed with combustible gas in a certain proportion.
  • Combustion (oxidation) of heated metal in the oxygen stream and removal of combustion products from the cutting zone.

If we consider the classification of only hand torches, the following features are of fundamental importance:

  • Type of fuel, power and method of obtaining a mixture of gases for heating flame;
  • Classification by type of combustible gas: acetylene, propane-butane, methane, universal, MAF;

Please note! kerosene torches and gasoline torches, though they have the same purpose, are fuel-powered torches

  • By capacity: low (cutting metal of thickness from 3 to 100 mm). marking P1, medium (up to 200 mm). P2, high (up to 300 mm). P3. There are samples with increased cutting thickness. up to 500 mm.
  • By the way of receiving combustible gas: injected and non-injected.

And if the first feature affects only the temperature of the heating flame, and power. the maximum thickness of the metal, the third feature is determined by the design of the torch.

Injector, or twin-tube, gas torch is the most common type of design. Technical oxygen in the cutter is divided into two flows.

Part of the flow through the upper tube moves into the head of the tip and comes out at high speed through the central nozzle of the inner mouthpiece. This part of the structure is responsible for the cutting phase of the process. Control valve or lever valve is located outside the body.

The other part goes into the injector. the principle of operation of which lies in the fact that the injected gas (oxygen), coming out into the mixing chamber at high pressure and high speed, creates there a rarefaction zone and draws flammable (ejected) gas through peripheral holes. Through mixing, the speeds are equalized and the outlet of the chamber produces a gas mixture with a velocity lower than that of the injected oxygen, but higher than that of the ejected combustible gas.Then the gas mixture travels through the lower pipe to the head of the tip, comes out through the nozzles between the inner and the outer mouthpiece and forms a plume of heating flame. Each channel has its own valve on the body that regulates the flow of oxygen and combustible gas into the injector.

manual, cutting, metal, necessary, equipment

The sparkless, or three-pipe torch has a more complicated design. both oxygen and gas flow to the head through separate tubes.

How to cut metal with an oxypropane torch

Metal cutting is necessary for dismantling metal structures, cutting any kind of rolled products before machining or welding. And if a sheet or profile of small thickness can be cut with a mechanical tool (with manual, electric or hydraulic drive). But to work with metal workpieces of great thickness you need a gas cutter, or in professional slang. autogenous. In this article the master plumber will tell you how to cut metal with an oxypropane torch.

Regardless of the size of the auto-gen and the type of heating gas mixture, metal cutting is performed due to metal combustion in a jet of pure oxygen pumped through the nozzle of the head into the working area.

Pay attention! The basic and fundamental condition of gas cutting is that the combustion temperature must be lower than the melting temperature. Otherwise, the metal, before it starts to burn, will melt and drain. Low-carbon steels meet this condition, while non-ferrous metals and cast iron do not

Most alloyed steels are also not amenable to gas cutting. there are restrictions on the maximum allowable doses of alloying elements, carbon and impurities, above which the process of metal burning in oxygen becomes unstable or is interrupted at all.The cutting process itself can be broken down into two phases:

  • Heating a limited area of the part to a temperature at which the metal begins to burn. And in order to obtain a plume of heating flame, some of the technical oxygen in a certain proportion is mixed with combustible gas.
  • Combustion (oxidation) of the heated metal in the oxygen jet, and removal of combustion products from the cutting zone.
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If we consider the classification only hand torches, then the following features are essential:

  • Type of fuel, power, and how to get the gas mixture for the warming flame;
  • Classification by the kind of combustible gas: acetylene, propane-butane, methane, universal, MAF;

Please note! kerosene torches and gasoline torches, even if they have the same purpose, are fuel-powered torches

  • For power: small (metal cutting from 3 to 100 mm thick). marking P1, medium (up to 200 mm). P2, high (up to 300 mm). P3. There are samples with increased cutting thickness. up to 500 mm.
  • By the method of obtaining combustible gas: injected and non-injected.

And if the first feature affects only the temperature of the heating flame, and power. the maximum thickness of the metal, the third feature is determined by the design of the torch.

Injector or two-tube, gas torch is the most common type of design. Technical oxygen in the torch is divided into two streams.

Part of the flow through the upper tube travels to the tip head and exits at high velocity through the central nozzle of the inner mouthpiece. This part of the construction is responsible for the cutting phase of the process. The control valve or lever valve is moved outside the housing.

The other part enters the injector. the principle of operation of which lies in the fact that the injected gas (oxygen), coming out into the mixing chamber at high pressure and high speed, creates there a rarefaction zone and draws flammable (ejected) gas through peripheral holes. Through mixing, the velocities are equalized and the outlet of the chamber produces a gas mixture with a velocity lower than that of the injected oxygen, but higher than that of the ejected combustible gas.The gas mixture then travels through the lower tube to the head of the tip, exits through nozzles between the inner and the outer mouthpiece, and forms a plume of heating flame. Each channel has its own valve on the body, which regulates the flow of oxygen and combustible gas into the injector.

The sparkless, or three-pipe cutter has a more complex design. both oxygen and gas flows to the head through separate tubes.

Manual gas welding and metal cutting.

Gas welding is carried out owing to heat, released at combustion of acetylene-oxygen mixture. When the flame temperature reaches 3150 °C, the edges of the pipes being joined and the filler material. welding wire of Sv-08 or Sv-08A grades. are melted. Acetylene for welding is supplied in cylinders or obtained on site in portable gas generators. In the first case, steel cylinders with a capacity of 40 or 50 litres and an initial pressure of 15-18 kgf/cm2 are used. To avoid acetylene explosion during transportation, the cylinder is filled with activated carbon porous mass, and acetylene is dissolved in acetone. In case of application of gas generators, acetylene is produced by decomposition of calcium carbide (CaC2) in water. The reaction proceeds according to CaC2 equation.j-2H20 = C2Ht.f- Ca(OH)2. For 1 kg of calcium carbide it is used 5-10 liters of water, thus 230. 280 liters of acetylene is formed.

Oxygen is delivered to the site of work in steel cylinders with a capacity of up to 40 liters at a pressure of 150 kgf/cm2. Remember, to avoid explosion, oxygen cylinders must not have contact with oil, oily gloves, or rags.

Reducers of ABO-5, ABD-5, ASO-10, ARD-30 types are used for pressure decrease of acetylene up to 0,1-1,5 kgf/cm2, and reduction of oxygen pressure is performed by pressure reducers of the following types

1. points with acetylene (in case of gas cylinder version); 2. acetylene reducer; з. gas generator (in case of the gas generator version); 4. Oxygen cylinder; 5. oxygen reducer; 6. rubber-fabric hoses; 7. burner or torch; 8. wire.

KBO-60, KBD-60, KBD-25, and KSO-U. The given designations are deciphered as follows: K. oxygen, A. acetylene, B. cylinder, P. ramp, C. network, O. one-stage, D. two-stage. Numbers after the designation indicate the gear capacity, cubic meters per hour.

Acetylene-oxygen mixture is obtained and combusted in manual welding torches type GS-2 and GS-3 with interchangeable tips. Gas and oxygen are supplied to the burner through rubber-fabric hoses 6 (Fig. VII.3) with internal diameters of 6, 9, 12 and 16 mm.

Units for gas welding are simple, transportable, universal, but the gas welding is accompanied by a burnout of the metal pipe carbon, manganese and silicon, which reduces the mechanical properties of gas welded pipes. Therefore gas welding is admissible only for gas pipelines up to 150 mm in diameter with wall thickness not exceeding 5 mm at gas pressure in the pipeline up to 3 kgf/cm2. In general, gas welding is used for installation of domestic gas pipelines of small diameters.

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When replacing the gas torch with a cutting torch, for example, “Plamya-62”, the unit can be used to cut metal. In the torches instead of acetylene the propane-butane., natural gas, kerosene, gasoline, etc.

Gas cutting is widely used at installation of shaped parts of gas pipelines, for cutting out defective joints and at taps of branches.

Automatic welding under a layer of flux. The peculiarity of flux-cored welding is that the welding arc, formed between the welded workpiece and the end of the filler wire, burns under a layer of loose flux composed of silicates of manganese, silicon or magnesium. The heat of the arc melts the edges of the welded product, the end of the filler wire and some of the flux. The light molten flux forms a gas and liquid slab over the molten metal bath, protecting it from exposure to air. In addition, the flux layers decouples the weld pool and slows down its cooling.

Automatic welding of gas pipelines is performed over the first (root) layer welded by hand. At the same time, the section of the tubes to be welded evenly rotates on the stand by the end rotator, and the welding machine (welding head), which is fixed over the joint to be welded, evenly supplies the welding filler wire and flux into the welding area.

Due to the increased welding current up to 900 А and a reliable flux thermal insulation, a large amount of heat is concentrated in the welding area, which provides deep penetration of the metal and slows down the cooling of the weld. This allows to reduce the number of welding layers (not counting the root layer) to two, and for small thicknesses of pipe walls to one layer, which significantly increases the productivity of welding.

Automatic submerged-arc welding unit consists of a DC or AC current source, a welding machine, a stand for assembly and welding of pipes (first layer) in a section and a welding stand with a section end rotator.

Gas-electric welding. At the present time electric arc welding in carbon dioxide medium is widespread in construction of gas pipelines, which is characterized by a powerful and stable arc discharge. The heat of the arc discharge melts the edges of the pipes to be welded and the end of the electrode wire fed into the welding zone. The resulting bath of molten metal is protected from the air by a cloud of carbon dioxide, which continuously flows through the nozzle of the electrode holder (Fig. VII.4).

On the stands, automatic gas-electric welding is used, which is similar to automatic welding under a layer of flux. In the trace conditions more convenient is semi-automatic gas-electric welding of rotary and not rotary joints, which technique does not differ much from technique of manual electric arc welding, as the electrocontroller on a welded product is moved manually (fig. VII.5).

As current sources for semi-automatic gas-electric welding DC generators or alternating current converters with capacity of 5-10 kW are used. For automatic electrode wire feeding and carbon dioxide supply to the electrode holder use hose semiautomatic devices A-547, A-607 and others with a remote switch-off button on the welder’s shield. The mode of semi-automatic welding of turning joints is as follows: welding current 180-200 a, arc voltage 24-26 V, carbon dioxide pressure on the reducer 1,5-2,0 kgf/cm2, wire feed speed 5-15 m/min.

Special torches

For foundries and the metal industry Messer offers special torches for oxygen and oxygen-flux cutting of large thicknesses as well as stainless steels, cast iron and non-ferrous metals. These torches feature an increased torch length to reduce the heat impact on the cutter, a reinforced design of the valve block and all other torch components, i.e.к. the cutting process takes place at higher gas pressures and at high gas flow rate. To ensure safety when working with such torches it is recommended to use reinforced hoses, a special oxygen reducer with a high flow rate up to 150 m 3 / h, and operator’s protective equipment.

Safety precautions

You need this protection against electric shock:

  • Grounding the machine.
  • Insulation of electrically conductive parts of equipment.
  • Dry, undamaged clothing.
  • Avoid working in wet weather.

Eye protection requires a special mask with light filters.

Gas welding is a threat of burns, explosions fires. Avoiding an emergency situation will help:

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