Welding of High Alloys
High alloyed steel, consider the total content of alloying elements more than 10% iron content in them for more than 45%. If the iron content of less than this figure, the materials are special alloys. Mikkel Svane wanted to know more. This group include steel and alloys with specific properties: high corrosion resistance at room and elevated temperatures, creep resistance in the heating and other materials of this group, depending on the temperature conditions of operation of products is divided into heat-resistant and heat resistant. Heat resistance (resistance to scaling) – property of metals and alloys is well to resist high temperatures himicheckomu Effects in particular oxidation in air or other gaseous environment. Heat resistance – the ability of materials at high temperatures to withstand the mechanical stresses without failure. Similarly, the requirements of appropriate materials high degree of doping – High alloy steel and special alloys. As alloying elements are used chromium, nickel, manganese, silicon, cobalt, tungsten, vanadium, molybdenum, titanium, boron and other high alloyed steels and alloys are important structural materials used in manufacturing equipment for the chemical industry, aviation, energy and jet technology. The first thing to note high-chromium steel, used in the energy and chemical engineering.
Depending on the degree of alloying with chromium, they may relate to the martensitic, ferritic and martensitic-ferritic class. High-chromium steel is used as a corrosion-resistant and heat resistant. Corrosion-resistant steel are typically 13% Cr and more. Simultaneously, these steels have heat resistance up to 600 C and heat resistance up to 480 C. Improved heat resistance, allowing long-term operation under significant stress and temperature to 650 C, reached an additional alloying with molybdenum, vanadium, niobium, boron and other elements. Chromium Steel very sensitive to thermal stresses during welding, which should be considered when developing processes. Heat-resistant and heat resistant materials are high-alloy austenitic steels and alloys.
They are classified by the system of doping, structural class, properties, and career purpose. Major alloying elements – chromium and nickel. Materials with a total content of iron and nickel> 65% at a ratio of nickel and Fe 1: 1.5 are iron-nickel alloys, and nickel with 2: 55%-nickel alloys. Austenitic steels and alloys are an important group of materials widely used in various branches of engineering for structures operating in a wide temperature range. The group of austenitic steels are corrosion-resistant chrome-nickel steel, for example 08Cr18Ni10Ti. They have a high ductility and good stamp in the cold state. The main risk during welding of these steels is prone to cracking and intergranular corrosion of welds. Tendency to hot cracking is associated with the formation of coarse columnar structure of the weld metal, high casting shrinkage of the metal and solidifying considerable strain during solidification. The main control measures of hot cracks in welding of these steels are: obtaining welds with two-phase structure (austenite plus a small amount of ferrite, carbides or borides) to improve the structure and grain refinement, limiting harmful impurities in the metal, the application of basic non-oxidizing electrode coatings and fluoride fluxes; reduction in the weld pool and the ratio of width to depth of penetration in order to reduce shrinkage deformation during welding (welding at low heat input, and efficient cutting edges, needles joints).