Welding materials: definition, characteristics, manufacturing, storage. Primary welding material

The connection of metal structures by welding is the most common method in construction, instrument making, the production of machines and mechanisms. In the process of welding, two surfaces are joined after melting the base metal under the action of heat. An additional surfacing element is used, which forms a welded seam after cooling and crystallization , or surfacing. The welding material is introduced into the working space by a consumable, current-carrying, non-consumable electrode or gas welding. In the process of work, welding materials perform the following work:

• When melting, moving in an arc, being in a bath, solidifying protect molten metal;
• Alloy and deoxidize the metal, regulating the chemical composition of the steels;
• Remove oxides, slags, phosphorus and sulfur from the filling of the seam;
• Free the suture from nitrogen and hydrogen.

Classification of welding materials

A large number of materials required for joining metals by welding make it difficult to accurately classify, but the main welding materials are divided as follows:

• Filler wire for welding and surfacing;
• For arc welding, piece electrodes;
• Wire and plate electrodes for slag welding;
• Additive additional materials of non-continuous, continuous, tubular section;
• Extruded wire rods, rolled, stretched cast rods and wire, surfacing tapes with powder coating;
• Flammable gas or oxygen;
• Welding equipment, compressor;
• Gas cylinders;
• A generator for the production of acetylene carbide from acetylene or an acetylene cylinder under pressure;
• Reducer for reducing the pressure of the welding gas;
• Burners for welding, quenching, fusing with a set of necessary types of tips of different diameters;
• Rubber hoses for moving oxygen;
• Fluxes and powders for welding.

Melting wires, plates and rods

This kind of electrodes is used for welding in protective gases, under a flux, electroslag. Steel wire, as a welding material, is divided into high-alloy, low-carbon and alloyed. In total, 77 kinds of similar products are determined by the assortment. Selecting the required brands, change the chemical composition of the seam. Usually a wire composition is used that is similar to a weld metal. The characteristic of the welding material must comply with GOST and is indicated on the package.

Alloyed and low-carbon steel for the production of wire are divided into copper plated and unmelted. For manual welding use a wire, chopped into pieces from 360 to 400 mm in length. It is delivered to the consumer with coils weighing from 20 to 85 kg. All coils are equipped with labels indicating the manufacturer and technical parameters of the wire.

Plates are used for electroslag welding. Arc manual welding is performed using an electrode metal rod with a special coating, called an electrode. The electrodes are divided according to the thickness and composition of the applied layer and the manufacturing quality. The thickness is distinguished by a particularly thick, medium and thin coating. Three groups in GOST are used for dividing the electrodes depending on the accuracy of production and the content of sulfur and phosphorus in the composition of the coating. The type of welding material with a coating of stabilizing, binding, deoxidizing, alloying components is indicated by the letters:

• Coating with acid additives - A;
• The main classical variant is B;
• Coating with the addition of cellulose - C;
• Mixed materials in the surface layer - P.

Non-melting welded rods and electrodes for machine welding

To connect surfaces in shielding gases, special welding materials are used. The definition of such welding is given as a process using an electric arc between the electrode and the surface as a source of heat. Round electrodes of tungsten with a diameter of 5-10 mm lead an electric current to the arc region. As a material, pure tungsten is used or additives of oxides of lanthanum, yttrium, sodium dioxide are added. Tungsten itself can not be replaced with cheaper metal, since it is the most refractory, with a high boiling point (5900 ºС) and is used for DC and AC welding.

Application of oxygen

Oxygen is heavier than air, it contributes to the combustion of gases and vapors at high speed, while heat is released and a high melting point is reached. The interaction of compressed oxygen with fatty oils and lubricants leads to spontaneous ignition and explosion, so work with oxygen cylinders is conducted in clean conditions, without the danger of such contamination. Storage of oxygen-type welding materials is performed in compliance with fire safety standards.

Oxygen for welding is technical, obtained from the atmosphere. Air is treated in special separation devices, carbon dioxide is removed, the final product is dried. Liquid oxygen for transportation and storage requires special containers with increased thermal insulation.

Use of acetylene

Acetylene is an oxygen compound with hydrogen. This combustible gas at normal temperature is in the gaseous state. The colorless gas contains impurities of ammonia and hydrogen sulphide. Dangerous is the flammable component of the material. Welding pressure of more than 1.5 kgf / cm ² or accelerated heating to 400 ° C is sufficient for an explosion. Gas is produced by an electric arc discharge, which facilitates the separation of liquid combustible components or decomposition of calcium carbide under the influence of moisture.

Gas substitutes for acetylene

Requirements for welding materials allow the use of a pair of liquids and other gases for work. They are used if the heating temperature exceeds twice the melting point of the metal. For combustion of different types of gases , this or that quantity of oxygen entering the burner is required. Combustible substances in place of acetylene are used because of their low cost and the possibility of widespread production. They are used in various industries, but the use of substitutes is limited by their relatively low heating limit.

Wire and welding fluxes

For welding, unidentified unidentified wire is not used. The surface of the filler wire is made smooth, free of rust, scale, grease. It is selected according to the melting index, which is below this characteristic for welded steels. One of the qualitative properties of the wire is its gradual melting without a sharp surge of sprays. As an exception, if there is no required wire, for the welding of brass, lead, copper, stainless steel, strips of cut metal from the same material that is connected are used.

When welding metals such as aluminum, magnesium, copper, brass, cast iron, there is an active interaction of colored casting with oxygen from the atmosphere or oxidizing flame. The reaction leads to the formation of oxides with a high melting point, which create a harmful film and make it difficult for the substance to transfer to the liquid state on the surface. A welding material called flux, consisting of a paste or a powder of appropriate composition, is used to protect the surface of the molten mass. The material is boric acid, calcined borax. Fluxes are not used for welding alloy steels.

Safety water closures

Devices for protecting the rubber pipeline and the gas generator from the return of the return fire from the burner are called the gate. Requirements for welding materials determine that the water seal is designed in such a way that does not ignite the oxygen or acetylene mass in the hole of the torch or torch. The water valve is always present in the equipment of the device, this is the requirement of fire safety, which is necessarily fulfilled.

The bolt is placed on the gap between the torch and the burner, according to the instruction it is in good order and periodically filled with water to the required level. This device is the main one in the welding equipment chain.

Cylinders for storage of compressed gases

Cylinders are made in the form of steel vessels of cylindrical shape. The tapered hole in the throat area is closed by a shut-off valve on the thread. The connection of the cylinder walls is carried out in a seamless manner, the material is alloyed and carbon steel. Outer coloring makes it possible to recognize the type of gas placed inside. Oxygen is transported in blue vessels, acetylene cylinders are painted white, yellow-green tinge indicates the hydrogen content, the remaining combustible gases are placed in red containers.

On the upper part of the cylinder write the passport data of gas. The requirement for storage of welding materials requires that the cylinders be installed vertically and secured to the wall with a yoke. The valves of oxygen storage cylinders are made of brass, the use of steels is not permitted due to corrosion of materials in the gaseous medium. Cranes of acetylene gas cylinders are made of steel, it is forbidden to use copper and an alloy with a copper content of more than 70%. Acetylene reacts with copper to form an explosive mixture.

Gas reducers

Such a welding material, like a reducer, serves to relieve the gas pressure from the balloon and maintain the indicator at a constant level throughout the entire operating time, regardless of the lowering of the head of the substance in the cylinder. Gearboxes produce two-chamber and single-chamber. The former work more productively, maintain a constant pressure and do not freeze with prolonged use of gas mixtures. To supply gas to the burner, there are rubber hoses with fabric gaskets, which pass a preliminary test for strength and holding pressure, as there are special documents. Separately, use hoses for oxygen and acetylene. For the supply of kerosene and gasoline, sleeves of a material resistant to gasoline are used.

Requirements for materials for welding

For any type of welding materials are used in accordance with strict standards, where the requirements for acceptance and control are clearly indicated. All parties that went to the manufacture of welding materials in the factory, are supplied with a certificate indicating the technical indicators:

• A trademark of the manufacturer;
• Conventional symbols consisting of letters and numbers showing the brand and type;
• Factory number of the melting and shifting lot;
• The index of the surface state of the electrode or wire;
• Chemical composition of the alloy indicating the percentage;
• Mechanical characteristics of the resulting welded seam;
• net weight.

A common requirement for all electrodes is a stably burning arc, a well-formed seam. The metal of the obtained surfacing corresponds to a predetermined chemical composition, the melting of the rod during operation proceeds evenly, without splashing and release of toxic substances. Wire promotes the production of high-quality welding, slag from the surface of the seam is removed easily, the seam coating is strong. The electrodes retain the technical parameters for a long time.

Every detail is important for the welding process. The use of high-quality materials in the work plays an important role in the process of stable and strong bonding of metals.