INFLUENCE OF WELDING TECHNIQUES ON MICROSTRUCTURE AND HARDNESS OF STEEL JOINTS USED IN AUTOMOTIVE AIR CONDITIONERS

Austenitic steels belong to a group of special-purpose steels that are widely used in highly aggressive environments due to their enhanced anticorrosive behavior and high mechanical properties. The good formability and weldability of these materials has made them very popular in automotive AC systems. This study presents the results of hardness tests and microstructure observations on plasma- and laser-welded joints. The examined joints consisted of two different stainless steel components; i.e., a nipple made from corrosion-resistant AISI 304 steel and a corrugated hose made from 316L steel. Microplasma welding was carried out on a workstation equipped with an MSP-51 plasma supply system and a BY-100T positioner. The laser-welded joint was made on a numerically controlled workstation equipped with an Nd:YAG laser (without filler material) with 1 kW of maximum power; the rotational speed of the welded component was n = 4 rpm. Microstructural observations were performed using a scanning electron microscope and an optical microscope. Vickers hardness was measured with a hardness tester. The obtained results proved that both the microplasma- and laser-welded joints were free from any visible welding imperfections. In the micro areas of the austenitic steel weld, crystals of intercellular ferrite appeared against a background of austenite. The crystallization front (depending on the welding technology) was running from the fusion line towards the weld axis. The grain size depended on the distance from the fusion line

Wykorzystanie promieniowania emitowanego przez łuk elektryczny do monitorowania procesu spawania metodą TIG rozprawa doktorska /

Tyt. z ekranu tytułowego.Praca doktorska. Akademia Górniczo-Hutnicza im. Stanisława Staszica (Kraków), 2010.Zawiera bibliogr.Dostępna także w wersji drukowanej.Tryb dostępu: Internet.Fotodetektory CCD, karty spektrofotometryczne, spawanie metodą TIG, parametry technologiczne procesu spawania metodą TIG, promieniowanie łuku spawalniczego, badanie promieniowania łuku spawalniczego, monitorowanie procesu spawania, metodyka prowadzonych badań, laboratoryjne stanowisko badawcze, badanie wpływu parametrów spawania w metodzie TIG na emitowane promieniowanie elektromagnetyczne, badanie wpływu zmiany natężenia prądu spawania i długości łuku spawalniczego w metodzie TIG na rozkład widma promieniowania łuku spawalniczego, analiza pików widmowych, badanie wpływu skokowej, płynnej zmiany długości łuku spawalniczego w metodzie TIG na natężenie promieniowania widzialnego łuku spawalniczego, stany przejściowe, badanie wpływu zmiany natężenia prądu spawania w metodzie TIG na natężenie promieniowania dla wybranych długości fali, wyznaczenie parametrów uogólnionego modelu teoretycznego na podstawie zależności natężenia promieniowania łuku spawalniczego TIG od natężenia prądu spawania, długości łuku spawalniczego, model teoretyczny, uogólniony, sztuczne sieci neuronowe, badanie wpływu gazu osłonowego na rozkład widma promieniowania łuku spawalniczego w metodzie TIG, badanie wpływu materiału rodzimego na widmo natężenia promieniowania łuku spawalniczego, badanie wpływu materiału dodatkowego na rozkład widma promieniowania łuku spawalniczego, badanie wpływu natężenia prądu spawania, prędkości podawania drutu spawalniczego przy spawaniu metodą TIG z materiałem dodatkowym na rozkład widma promieniowania łuku spawalniczego, badanie wpływu rodzaju materiału dodatkowego na rozkład widma promieniowania łuku spawalniczego, badanie wpływu zakłóceń procesu spawania na rozkład widma promieniowania łuku spawalniczego, monitorowanie procesu spawania metodą TIG z wykorzystaniem promieniowania łuku spawalniczeg

THE NUMERICAL INVESTIGATION OF THERMAL CYCLE OF LASER SURFACE HARDENING

Subassemblies of machines and devices must be characterized by appropriate exploitation features, especially in relation to the surface layer of cooperating surfaces. Structure and properties of these layers ensure appropriate resistance to abrasive, corrosive and fatigue wear and determine the operating life and failure-free cooperation of these components. Specific antiwear characteristics of surface layers can be obtained using many different manufacturing techniques. The current techniques include treatment with a concentrated energy beam, e.g. laser beam. The essence of the laser beam surface hardening process is the introduction of a sufficient amount of heat into the workpiece material as a result of the absorption of the laser radiation and the cooling of the surface as a result of heat conduction deep into the material (usually no additional cooling media are used for cooling). A necessary condition is an adequate heat capacity of the workpiece. The hardening process with concentrated energy beams does not require heating of the entire workpiece. The workpieces are only heated in the surface layer. A precisely defined and locally limited heat affected zone means that the amount of heat introduced into the material is very limited. Solving technical problems of surface hardening is often aided by numerical methods, among which the finite element method (FEM) is the most commonly used. In this study, FEM numerical models of the laser hardening process were developed. It was determined the heat capacity of the workpieces sufficient to achieve the required thermal cycle at the workpiece specific locations. It was also determined the influence of the heating path sequence and the time delay between them on the thermal cycles

Wpływ metody spawania na mikrostrukturę i właściwości mechaniczne złączy ze stopów aluminium

Rapid technological progress in recent years has led to an intensified interest in alternative methods of joining metals. Today’s industry is constantly demanding new joining processes, which enable high-quality welded joints in a wide range of thicknesses of combined materials at low production cost. There are at least several dozen welding methods currently available. The selection of the process depends on the type of welded materials, acceptable heat input, as well as future working conditions. The paper presents the results of the microstructural examination and mechanical properties of joints of the aluminum alloy for plastic working such as EN AW-6082. The paper presents the results of microstructural observations and mechanical properties of EN AW-6082 aluminum alloy. Methods used for joining were successively TIG (welding with a non-consumable electrode in a shield of inert gases), MIG (welding with a consumable electrode in a shield of inert gases), EBW (electron beam welding) along with FSW (friction stir welding method). TIG (welding with a non-consumable electrode in a shield of inert gases), MIG (welding with a consumable electrode in a shield of inert gases), EBW (electron beam welding) along with FSW (friction stir welding method) were used as joining techniques.Współczesny przemysł wymaga opracowania i udoskonalania metod, które umożliwiają uzyskanie wysokiej jakości połączeń w szerokim zakresie grubości łączonych materiałów oraz obniżenie kosztu produkcji. Istnieje kilkadziesiąt metod spawania. Proces ten trzeba dostosować do rodzaju spajanych materiałów, dostępnych źródeł energii, a także do przyszłych warunków pracy urządzeń. W pracy przedstawiono wyniki badań łączenia najpopularniejszego stopu do przeróbki plastycznej, jakim jest stop EN AW-6082. Metodami wykorzystanymi do łączenia były zarówno najbardziej popularne techniki spawania: TIG (spawanie elektrodą nietopliwą w osłonie gazów obojętnych), MIG (spawanie elektrodą topliwą w osłonie gazów obojętnych), metoda wysokoenergetyczna EBW (spawanie wiązką elektronową), jak również metoda zgrzewania tarciowego z mieszaniem materiały zgrzeiny – FSW

Microstructure and Properties of Dissimilar Joints of AISI 430 Steel with Inconel 625 Obtained by Electron Beam Welding

Electron Beam Welding (EBM) is a high-energy density fusion process where joint is bombarded to be welded with strongly focused beam of electrons. This method is often used for advanced materials and complex, critical parts, like turbine rotors, but it can also be used for many simpler processes involving large production runs. It is very suitable for butt welding materials of different thicknesses. The aim of this work was to study the microstructure, hardness, and electrochemical corrosion behavior between the dissimilar welds were investigated. Electron Beam Welding of dissimilar steel alloys Inconel 625 and AISI 430 was studied. In welding process there was used only welded materials without filling material. Results showed the microstructure of the weld solidified in dendritic morphology. The microstructure of fusion zone showed that dendrites grew in different directions for each grain. The dendrites and columnar grains are mainly exposed to the fusion boundary with some equiaxed grains. The hardness of the overall joint was non-uniform. The highest hardness of the HAZ/Inconel 625 (the heat-affected zone) was 258 HV, and the lowest weld zone hardness was 178 HV. The decrease in weld hardness may be due to the linear welding energy, which led to grain growth and excessive cooling. HAZ/AISI 430 steel has the lowest current density and the highest corrosion potential. Steel has a more negative corrosion potential and a lower corrosion current density than joints, likely due to higher levels of chromium. In this study, a metallographic investigation of the joints revealed no defects such as microcracks or pores. The melting temperatures of the two materials were quite different, but with the help of gravity, stainless steel acts as a permanent joint, like a rivet

Semi-Hybrid CO2 Laser Metal Deposition Method with Inter Substrate Buffer Zone

This article presents the results of the metal deposition process using additive materials in the form of filler wire and metal powder. An important problem in wire deposition using a CO2 laser was overcome by using a combination of the abovementioned methods. The deposition of a multicomponent alloy—Inconel 625—on a basic substrate such as structural steel is presented. The authors propose a new approach for stopping carbon and iron diffusion from the substrate, by using the Semi-Hybrid Deposition Method (S-HDM) developed by team members. The proposed semi-hybrid method was compared with alternative wire and powder deposition using laser beam. Differences of S-HDM and classic wire deposition and powder deposition methods are presented using metallographic analysis, within optic and electron microscopy. Significant differences in the obtained results reveal advantages of the developed method compared to traditional deposition methods. A comparison of the aforementioned methods performed using nickel based super alloy Inconel 625 deposited on low carbon steel substrate is presented. An alternative prototyping approach for an advanced high alloy materials deposition using CO2 laser, without the requirement of using the same substrate was presented in this article. This study confirmed the established assumption of reducing selected components diffusion from a substrate via buffer layer. Results of metallographic analysis confirm the advantages and application potential of using the new semi-hybrid method for prototyping high alloy materials on low alloy structural steel substrate

Semi-Hybrid CO₂ Laser Metal Deposition Method with Inter Substrate Buffer Zone

This article presents the results of the metal deposition process using additive materials in the form of filler wire and metal powder. An important problem in wire deposition using a CO2 laser was overcome by using a combination of the abovementioned methods. The deposition of a multicomponent alloy—Inconel 625—on a basic substrate such as structural steel is presented. The authors propose a new approach for stopping carbon and iron diffusion from the substrate, by using the Semi-Hybrid Deposition Method (S-HDM) developed by team members. The proposed semi-hybrid method was compared with alternative wire and powder deposition using laser beam. Differences of S-HDM and classic wire deposition and powder deposition methods are presented using metallographic analysis, within optic and electron microscopy. Significant differences in the obtained results reveal advantages of the developed method compared to traditional deposition methods. A comparison of the aforementioned methods performed using nickel based super alloy Inconel 625 deposited on low carbon steel substrate is presented. An alternative prototyping approach for an advanced high alloy materials deposition using CO2 laser, without the requirement of using the same substrate was presented in this article. This study confirmed the established assumption of reducing selected components diffusion from a substrate via buffer layer. Results of metallographic analysis confirm the advantages and application potential of using the new semi-hybrid method for prototyping high alloy materials on low alloy structural steel substrate