Mechanical Properties Of Weld Zone Research Articles

Performance Test of Weld Zone of Rotary Friction Welding of Titanium Alloy Drill Pipe

With the development of complex oil and gas reservoirs, it is difficult for traditional carbon steel to meet the requirements of drill pipe materials in drilling process. Titanium alloy has gradually become a new choice of drill pipe material because of its low density and good corrosion resistance. Titanium alloy has poor weldability and weld zone of titanium alloy drill string is easy to become initial defect and lead to drill pipe failure. Therefore, it is essential to evaluate the performance of titanium alloy drill pipe weld zone. In this paper, the weld zone of titanium alloy rotary friction welding is tested. Metallographic structure, hardness, tension and impact mechanical tests, fracture toughness evaluation and bending fatigue test are carried out. The test results show that the metallographic structure of weld zone changes under the influence of temperature, resulting in different mechanical properties of weld zone from that of pipe body zone. The yield strength and tensile strength in the weld zone are higher than those in the pipe zone, but the fracture toughness is lower than that in the pipe zone. The fatigue life of specimens in weld zone is more than 107 in drilling mud environment. In general, the mechanical properties of weld zone meet drilling requirements.

Mechanical properties of quenched and tempered steel welds

Abstract Welding is the most commonly used joining process in the industry. Generally, weld zone consists of three different regions such as base metal, heat-affected zone (HAZ) and weld metal (WM). Microstructure of HAZ and WM changes due to the heat effects after the welding process. These effects cause changes in mechanical properties such as Young modulus, tensile strength and hardness in weld zone. The aim of this paper is to identify the mechanical properties of weld zone by uni-axial tensile test, nanoindentation test and hardness test. For this aim, quenched and tempered steel plates were chosen as a test material having high strength. These plates were welded together by flux-cored arc welding method. To determine the effect of weld pass number on the mechanical properties, the weld was completed in single and multi-pass (MP) butt welds separately. For experiments, tensile test specimens were cut by plasma cutting method according to related standard on welded plates. These specimens were subjected to three different post weld heat treatments (PWHT) such as 200 °C, 300 °C and 400 °C to evaluate the hardness change in HAZ. The effect of weld-pass number and PWHT on mechanical properties such as Young modulus, tensile strength and hardness were obtained from WM and HAZ by uni-axial tensile test and nanoindentation test and compared to each other. The yield and ultimate tensile strength of weld zone of welded tensile test specimens (WTTS)-2 is lower than WTTS-1 due to MP welding process. Furthermore, the strain behaviour of weld zone is not affected by PWHT significantly.

Investigation on the influence of weld position on the deformation behavior of welded tube during free bending process

The plastic deformation behavior of welded tube is affected by the non-uniform distribution of the mechanical properties of welded tube during the free bending process. To explore the influence of weld position on the forming quality and axis dimensional accuracy of welded tube, the free bending experiment and numerical simulation of welded tube were conducted in this paper. First, the principle of free bending was theoretically deduced and the stress distribution of bent tube was analyzed. Then, the hardness test and uniaxial tensile test were conducted to obtain the mechanical properties of weld zone and parent zone of welded tube. The material strength in the weld zone of welded tube is significantly higher than that in the parent zone. Finally, the free bending experiment and numerical simulation with different weld positions were carried out, and the influence of weld position on the bending radius, cross-sectional distortion, and wall thickness of bent tube was discussed. All these findings advance the insight into the free bending deformation behavior of welded tube and help to improve the forming quality of welded tubes and facilitate the application of free bending technology in welded tube.

Effect of rhenium content on microstructures and mechanical properties of electron beam welded TZM alloy joints

In order to strengthen weld zones of molybdenum-titanium-zirconium (TZM) alloy joints, electron beam welding experiments using rhenium (Re) addition into weld metals were conducted. The effect of Re content on the phase constitution, microstructural evolution, and mechanical properties of weld zone was investigated by optical microscope (OM), scanning electron microscope (SEM), electron backscattering diffraction (EBSD), transmission electron microscope (TEM), microhardness and tensile tests. Weld narrowing and grain refinement were produced in the welded TZM alloy joints by adding Re interlayers. Re-rich particles segregated in grain boundaries and led to the promotions of stress relaxation and cohesive forces of GBs. Besides, low-angle grain boundaries emerged and increased with Re contents in weld zones, which can hinder the initiations and expandings of microcracks. Consequently, the tensile strengths of the joints were enhanced with the increasing Re contents in weld zones. When the Re content in the weld zone reached 48.7 wt. %, the tensile strength of the joint can be up to 524 MPa and the fracture location was also transferred from weld zone to heat affected zone.

Effect of Friction Stir Processing on Microstructure and Mechanical Properties of AZ91C Magnesium Cast Alloy Weld Zone

In this study, friction stir processing (FSP) was applied to the GTAW (TIG)-welded AZ91C cast alloy to refine the microstructure and optimize the mechanical properties of the weld zone. Microstructural investigation of the samples was performed by optical microscopy and the phases in the microstructure were determined by x-ray diffraction (XRD). The microstructural evaluations showed that FSP destroys the coarse dendritic microstructure. Furthermore, it dissolves the secondary hard and brittle β-Mg17Al12 phase existing at grain boundaries of the TIG weld zone. The closure and decrease in amount of porosities along with the elimination of the cracks in the microstructure were observed. These changes were followed by a significant grain refinement to an average value of 11 µm. The results showed that the hardness values increased to the mean ones, respectively, for as-cast (63 Hv), TIG weld zone (67 Hv), and stir zone (79 Hv). The yield and ultimate strength were significantly enhanced after FSP. The fractography evaluations, by scanning electron microscopy (SEM), indicated to a transition from brittle to ductile fracture surface after applying FSP to the TIG weld zone.

The Influence of Processing Parameters on Mechanical Properties and Microstructure of Welding Zone for Ti<sub>3</sub>Al-TC4 Dual Alloy

It has been investigated that the influence of processing parameters on mechanical properties of weld zone for Ti-24Al-15Nb-1.5Mo and TC4 dual alloy welded by electron beam in vacuum. The results shows the remarkable influence factors are heat treatment regime and deformation for yield strength of welded dual alloy samples at room temperature tensile test, and the remarkable influence factor is forging temperature for the elongation in tensile test at 500°C. From the combined analysis about other properties at room temperature and 500°C, the microstructure of the weld seam, it can been gotten the optimum parameters of processing dual alloy, i.e. forging at 1020°C, soaking for 12 hour at 700°C, air cooling, about 40% deformation and using billet of rolling state.

溶接軟化域を考慮したアルミニウム圧縮材の座屈耐力評価

On the aluminum alloy, the mechanical properties of weld zone are different from the base metal by welding heat. The purposes of this study are to explain the buckling behavior and to propose the buckling strength formula of the aluminum compression member with weld softening zone by experiment and analysis. Experimental parameters are cross-sectional shape, slenderness ratio, welding position, numbers of weld point and materials. From the experiment and analysis, the effects of the weld softening on the buckling strength are evaluated quantitatively and effective parameters are determined. The buckling strength design formula is proposed considering these effective parameters.

Ａｌ‐５％Ｍｇ合金鋳物の電子ビーム溶接に関する一研究

In electron beam welding of Al-5%Mg alloy casting (JISH5202, Class 7 AC7A), effects of factors such as welding conditions, base metal thickness (6, 16 mm), Ti addition (Ti free, 0.12%Ti) and etc. on welding phenomena, metallurgical and mechanical properties of weld zone have been investigated by microscopic observation, thermal cycle measurement, grain size measurement, fatigue test and etc. The results obtained are as follows:(1) In welding of AC7A with 6 mm thickness, arcing phenomena are reduced by proper welding condition and weld zone with sound mechanical properties are obtained. In welding AC7A (Ti) with 6 mm thickness, arcing phenomena are prevented by beam current at 5% down of filament current and weld zone with sound mechanical properties are obtained.(2) In welding of AC7A and AC7A(Ti) with 16 mm thickness, arcing phenomena are prevented by combined conditions such as low power density of beam (ab; 1.2), preheating (130°C) by EB passes and beam current at 5% down of filament current and weld zone with sound mechanical properties are obtained.(3) Intercrystallrne cracks in HAZ are observed with AMA, 16 mm thickness welded joints. Eutectic compositions (mainly Al3Mg2) with low melting point are recognized in intercrystalline cracks in HAZ.(4) Al-5%Mg alloy casting with 0.12%Ti addition shows good weldability owing to refined grain size of base metal and HAZ.

ユニオンアーク溶接用ワイヤに関する研究

We made a welding experiment on the combination of CS type flux and 6 kinds of wire with different chemical compositions, to examine the usability of wire and the mechanical properties of weld zone, by Unionarc method.Test pieces were butt joints of 12 mm thick plates, horizontal fillet welded tee joints of 9 mm thick plates with 6 mm fillet and all weld metal test specimens of 19 mm thick plates.The results of this study show that wires Y-B, Y-C and S 2 will be suited for welding of mild steels, HT 50 and HT 60.

オーステナイトMn鋼の熔接性におよぼす母材中の燐の影響

Several austenitic manganese steels differing in phosphorus content (0.024-0.085% and 0.276%) are welded with austenitic electrodes (Cr-Ni, Mn-Cr and Mn-Ni type), and mechanical test, slit type crack test and microscopic inspection on the weld zone are carried out.Under increased phosphorus content in parent metal, mechanical properties of weld zone are deteriorated and the hot-cracking tendency of weld metal and heat-affected zone is promoted. Phosphorus-rich, low-melting point eutectic in grain boundary is presumed to be responsible for these adverse phenomena.On the results of this investigation, authors deem it desirable from the standpoint of weldability to limit the maximum phosphorus content of austenitic manganese steel to 0.05%.