When connecting work pieces with certain parameters, the main task is to preserve the structure and properties of the material in the weld zone. In violation of the temperature regime, crystallization cracks and pores may occur, which leads to a loss in the quality of the connection. To avoid negative consequences, alloy steel is welded with specific electrodes in compliance with the temperature cycle, which avoids loss of quality. We will talk about technological methods and features when working with these materials.
Types of steels with additives and their properties
With the help of alloying additives, certain qualities are given to the alloy, such as heat resistance, low degree of corrosion, resistance to shock loads and aggressive environments. In these alloys there are various chemical elements and their percentage and determines the quality of the metal. They contain chromium, nickel, tungsten, vanadium, manganese, niobium and titanium, as well as their combinations, which determine the degree of characteristic physical qualities. As a result, the content of impurities in certain percentages determines the weldability of alloy steel of a certain grade.
According to the given physical properties and chemical composition, this type of material is divided into the following types:
- low-alloy grades in which the presence of impurities does not exceed 2.5%, while the carbon content in the metal is not taken into account;
- metal of medium alloyed composition, where additional elements occupy from 2.5% to 10% of the metal composition;
- high alloy steel with more than 10% special elements.
When welding this type of metal, it is extremely important to know the steel grade as accurately as possible in order to obtain a high-quality, strong and durable weld without breaking the structure of the work piece material. a welder need to understand the welding procedure specification.
The dependence of the weldability of parts that are alloyed with low and medium amounts of chemical additives on the content of carbon, silicon and manganese implies the use of electrodes of a certain type. It is also necessary to clean the joints from contaminants and traces of corrosion, a cycle of annealing of electrodes up to 400 ° C is mandatory, and workpieces are heated up to 200 ° C. An alloy with high alloying must be connected with a low value of welding currents, in order to avoid overheating of the starting materials.
Technological features of welding specific steels
The connection of special metals requires a special approach that will avoid overheating of the work pieces in the weld zone and loss of quality of the connection by removing the necessary components from it. It is necessary to use electrodes or welding wire with special properties and chemical composition. In addition, there are technical solutions such as plasma welding , which provides strength only in the weld zone, without overheating of the nearby metal thickness. Thus, high-quality welding of alloy steels can be carried out in a variety of ways.
Solutions for low weldability of alloys with special properties include:
application of new technical approaches such as the use of the plasma method of work;
the use of a low welding current density using inverter methods in a protective or active gas environment;
the connection of metals under flux, which is selected taking into account the properties of the work pieces;
selection of special coated electrodes close in composition to the welded composition and selection of the mode of operation and local calcification of parts, eliminating overheating of the alloy with a loss of its qualities.
It is important to note that each of these approaches requires the study of reference books and a scientific approach to the problem of combining alloys with various physicochemical parameters.
Methods of welding alloyed compositions depend on the brand and involve the use of metered welding currents, temperature conditions for the preparation of work pieces, as well as the chemical composition of the coated electrodes or welding wire. These solutions are described in detail in the manual for joining similar parts according to their properties.
The technology for welding alloy steels is not particularly complex if the composition of the work pieces and the welding mode are observed. These techniques are described in Code, Standard and manuals in sufficient detail, therefore, following them you can get high-quality and durable connection of this type of materials.