Different Zones Of Welded Joint Research Articles

Using the Method of Measuring the Microhardness of Different Zones of Welded Joints to Assess the Strength Properties

Corrosion-resistant steels with a high nitrogen content are used as structural materials for high-load critical products. Their high strength and ductility, austenite stability, corrosion and wear resistance are highly relevant for parts and structures operating in marine environments. In addition to a high level of operational properties, they are subject to the requirement of manufacturability, including weldability. Welding of such steels, due to the high concentration of nitrogen, is a complex technological operation, and it is necessary to avoid the appearance of gas nitrogen pores, hot cracks, a sharp drop in mechanical properties in any zones of welded joint. In this work, we investigated the regularities of changes in microhardness in different zones of welded joints (base metal, heat-affected zone of the weld, fusion zone and weld metal) of two grades of austenitic Cr-Ni-Mn-Mo-N high-strength steels with a high equilibrium nitrogen content (up to 0.6%). They fundamentally differ in the structural state of the base metal being welded: deformed (hot-rolled sheet) and cast (metal of a heat-treated cast plate). It has been shown that despite the use of different welding methods (MIG, MMA and TIG), the options for welding fillers and the type of weld groove, there are general patterns for each of the two types of base metal. The work also evaluated the correlation between these regularities and such basic characteristics of the structure and properties of rolled and cast metal of welded joints, such as the grain size and values ​​of the yield stress.

Effects of Preheating and Cooling Rate on the Microstructure and Mechanical Properties of Tungsten Inert Gas Welded Joints of AA5083-H321 Aluminum Alloy

Various preheating treatment and cooling rates conditions were carried out in Tungsten Inert Gas welding to study mechanical behavior and microstructural evolution of AA5083-H321 aluminum alloy welded joints. The microstructural analysis illustrated the diverse grain size during welding at different preheating and cooling rate. The highest preheat temperature caused to enlarge dendritic grains and during the fastest cooling rate formed the smaller grains. Also, the texture and grain size impressed on tensile behavior and hardness welds. Grain structure of the heat-affected zone, partially melted zone, and weld metal appeared to have a tangible relationship with preheating and cooling rate conditions. The microhardness of these regions increased by increasing the cooling rate and decreasing the preheating temperature. The high preheating had a negative effect on the hardness and width of different zones of welded joints. The results showed that the cooling rate has remarkable effects on the mechanical properties of the welded specimen.

Investigation on the Effect of Tool Pin Profiles on Mechanical and Microstructural Properties of Friction Stir Butt and Scarf Welded Aluminium Alloy 6063

In the present study, friction stir welding (FSW) of butt and scarf joints of Al 6063-T6 were investigated. Five different tool pin profiles (cylindrical, tapered cylindrical, square, triangular, and hexagonal) were applied for performing welding. Scarf joint, being a new joint configuration, was used and effect of pin profiles was investigated on this type of joint configuration. The effect of pin profiles on microstructure, micro-hardness, impact and tensile properties of friction stir welded Al 6063-T6 was investigated. Scanning electron and optical microscopy were employed to characterize the different zones of welded joints. A thorough discussion on correlation between mechanical properties and microstructure has been made. In addition, the formation of various defects during the FSW was discussed with the help of fractography of the fractured surfaces.

Microstructure and Salt Fog Corrosion Behavior of AA2219 Friction-Stir-Welded Aluminum Alloy

Plates (8.1-mm-thick) from aluminum alloy AA2219-T87 are studied after friction stir welding. The plates are subjected to salt fog corrosion tests according to ASTM B117 at different pH values and different spraying times. The regions affected by corrosion are studied in different zones of welded joints by the methods of optical and transmission electron microscopy. The corrosion resistance is determined in acid, basic and neutral solutions. The resistances of the base metal and of the zones of welded joints are compared.

Effect of the thermal cycle of welding on impact toughness components of different zones of welded joints in 10G2SB and 10G2SFB steels

Investigations were carried out to determine the effect of average heat input (3.6–16.3 kcal/cm) in automatic arc welding on the work of initiation ai and propagation ap of a ductile crack in different zones of welded joints in the 10G2SB and 10G2SFB steels in the condition after strengthening by heat treatment and after controlled rolling. Beads were deposited on 20 mm × 250 mm × 300 mm plates by automatic arc welding under FI-16 flux using Sv-10GNMA wire with a diameter of 5 mm. It is shown that increasing average heat input results in a decrease of the values of ai and ap. For the case in which an inflection point appears on the KCU–B curves (here B is the ductile component on the fracture surface of the impact specimens), it is proposed to approximate this curve by two linear sections. The point of intersection of the straight lines corresponds to the boundary of the heat-affected zone (HAZ). The experimental results also show that the mean-weighted estimate of the values of ap in the HAZ and in the parent metal are closely linked by the linear dependence , where T50 is the critical brittleness temperature, corresponding to the appearance of 50% of the ductile component on the fracture surface of the specimens.

Corrosion of welded joints of bimetallic composite tube in simulated offshore gas field environment

Purpose – The purpose of this investigation was to research the corrosion behavior of welded joints of bimetallic composite tube (X65/316L) welded with Inconel 625 in simulated sea water and in simulated production water, respectively. Design/methodology/approach – The different electrochemical corrosion and galvanic corrosion behaviors of different welded zones were identified using the dynamic potential scan method and galvanic corrosion technique. Findings – The heat-affected zone (HAZ) of welded joints was the most critical zone for corrosion. The closer to the welding line, more severe was the corrosion that was evident in the HAZ at room temperature. In welded joints of X65 tested in simulated seawater, tremendous corrosion occurred in the HAZ, followed by the base metal, and finally the welding line. However, there were few differences in corrosion of the different zones of welded joints in 316L in simulated production water. In such joints of 316L, corrosion comparatively attacked more easily to the HAZ. In galvanic corrosion tests, tremendous galvanic corrosion was evident on welded joints on X65, but comparatively slight gavanic corrosion appeared at welded joints in 316L. With the increased temperature, galvanic corrosion of welded joints was enhanced. Originality/value – The results can provide reference for reducing the gavalic corrosion of welded bimetallic composite tube metal in the actual operation.

Effect of the structure and stress state on the magnetic properties of metal in different zones of welded pipes of large diameter

The existence of an extensive network of main pipelines, both already operating and being constructed, which are exploited under complex climatic conditions, specifies the need for the development of methods of a nondestructive control for testing the current state of both the pipes themselves and the welded joints in the process of manufacture and subsequent service. In this work, we give the results of microstructural studies, as well as the mechanical and magnetic properties of different zones of welded joints (base metal, heat-affected zone, and the weld) of pipe steels of the strength classes X70 and X80 produced using the method of controlled rolling. The influence of different modes of loading on the magnetic characteristic of the metal of all three zones of welded joints has been investigated. The magnetic parameters that unambiguously characterize changes in the stress-strain state of the separate zones of the welded joint (weld, heat-affected zone, base metal) have been determined in certain ranges of the applied stresses.

Homogenisation approach in analysis of creep behaviour in multipass weld

Different zones of welded joints are subjected to different temperature fields during the process of welding. Furthermore, in multi-pass welding, heating and cooling cycles, which occur due to the overlap of the pass beads, lead to the formation of complex microstructures. A method of evaluating the creep response of a multipass weld based on the micromacro mechanics approach is introduced. Multipass weld microstructures consisting of a columnar zone, which can be related to the microstructure of a single pass weld, and a heat affected zones are considered. To model the microstructure of the multipass weld metal the representative volume element (RVE) method is employed. Numerical tests on one-component loading of the RVEs are performed and creep material properties for equivalent weld material reported for welds with different number of passes.

STRENGTH AND FRACTURE TOUGHNESS OF THE WELDED JOINTS MADE OF HIGH-STRENGTH FERRITIC STEEL

Abstract The paper presents experimental results of the characteristics of strength and fracture toughness of the material from the different zones of welded joints made of different participation of the linear welding energy. Strength characteristics and fracture toughness were determined in the weld material, in the area of fusion line, in the material of the heat affected zone and in the base material

Influence of Soil Corrosion and Transported Products on the Service Life of Welded Joints of Oil and Gas Pipelines

We develop methods for the evaluation of the service life of welded joints of the pipes of oil and gas pipelines taking into account the action of the main operating factors on the corrosion rate. We quantitatively analyze the influence of hydrogen released from the transported products on the rate of soil corrosion and residual life of different zones of welded joints of underground pipes.

A Simplified Determination of Creep Properties of Steels by Measuring their Crack Opening Displacements (COD) at Elevated Temperatures

The testing of creep resistance (for example σ1%/100000 h) of metals has been required for a long time (about 10 years) and some methods have been worked out to decrease testing time. The application of these methods has some difficulties. Now we have worked out a new empirical method to reduce testing time, namely COD measuring at an elevated temperature. The paper presents this method, which makes it possible to determine creep properties by measuring the materials COD at an elevated temperature. To determine COD we use notched samples with different radii and we tear them at an elevated temperature. The determination of COD is based on the Czoboly Radon method. By opening three different radii notches we approximate to zero radius which gives the COD. Master Curves of COD and creep resistance connections were drawn at 500 °C, which is not dependent on materials and they can be used for determining Creep Properties from COD measured at 500 °C. This method can be used for the comparison of the creep resistance of materials and for that of the creep properties of different zones of welded joints. The method is found useful in technical practice.

Influence of the inhibitor treatment on the corrosion resistance of different zones of welded joints

Influence of the inhibitor treatment on the corrosion resistance of different zones of welded joints