Composition Of Base Metal Research Articles

Crack-Tip Opening Displacement of Girth Welds in a Lean X70 Pipeline Steel.

Crack-tip opening displacement (CTOD) tests were conducted on girth welds of two API 5L X70 pipeline steels (pipe A and pipe B) to investigate the influence of base metal composition on the fracture toughness of the joint. CTOD measurements across the weld showed that the weld fusion zone had the lowest CTOD values for both pipes, with pipe B having a higher CTOD value than pipe A. Detailed microstructure characterization of the multi-pass weld showed that the fusion zone in both pipes consisted of three distinct zones: the columnar zone, the coarse equiaxed zone, and the fine equiaxed zone. Both the columnar zone and coarse-grained equiaxed zone had acicular ferrite and grain boundary ferrite microstructures, whereas the fine-grained equiaxed zone had a finer ferrite microstructure compared to the other two zones. The main difference between the two pipes was the variation in ferrite grain sizes and the volume fractions of grain boundary ferrite and acicular ferrite. In comparison to pipe B, pipe A, with a higher concentration of Mo, Ni, and Cu in both the base metal and the weld fusion zones, consisted of a higher volume fraction of grain boundary ferrite and a lower volume fraction of acicular ferrite in the columnar and coarse-grained equiaxed zones. The lower concentration of Mo, Ni, and Cu in pipe B likely resulted in the formation of a predominantly acicular ferrite microstructure in the fusion zone, thereby improving the toughness of the weld joint in comparison to pipe A.

INTEGRATING REMOTE SENSING DATA WITH HYDROTHERMAL ALTERATION MAPPING AND GEOCHEMICAL CHARACTERISTICS OF PRECAMBRIAN ROCKS ACROSS MAMBILLA PLATEAU, NORTHEASTERN, NIGERIA

Mineral exploration must include the mapping of hydrothermally altered regions, which are typically connected to mineralization. This study presents a strategy for integrating remote sensing data with the geochemical characteristics of Precambrian rocks from the Mambilla Plateau in northern Nigeria. Tectonically, the lineaments were fractures with the following orientations: NE-SW, NW-SE, ENE-WSW, and N-S. The distinct spectral reflectance and absorption properties of remotely sensed Landsat 8 data in the visible, near-infrared, shortwave-infrared, and thermal infrared portions of the electromagnetic spectrum were exploited in various digital image processing approaches. Mapping hydrothermal alteration minerals was done effectively and efficiently using band ratios (red/blue, SWIR 2/NIR, SWIR 1/NIR), spectral band combinations (Kaufmann and Sabins ratios), and principal component analysis. Ferric, phyllic, propylitic, and argillic iron all underwent changes as a result of hydrothermal alteration. Regional metamorphism also resulted in important alteration processes such as epidotization, sericitization, muscovititization, kaolinitization, and chloritization. Geochemically, on average, the Al2O3, SiO2, Fe2O3, CaO, MgO, K2O, Na2O, Li2O content are 12.04 %; 54.83%; 4.76%, 7.16%, 3.02%, 10.22%, 4.53%, 1.35% while MnO, P2O5 and TiO2 are less than 1%. The average base metal composition revealed that 60% of them had positive anomalies, which indicate mineralization, and 40% had negative anomalies. About 50% of the samples had positive anomalies, which indicated strong potential for harbouring mineralization based on the makeup of trace elements. Geochemical studies revealed the presence of lithium, titanium, and silica oxides in substantial concentrations. The local mineralization is governed by structural factors.

Noble and base metal geochemistry of late- to post-orogenic mafic dykes from central Spain

The post-tectonic and post-orogenic mafic rocks from the Spanish Central System (SCS) (Iberian Massif) include dyke swarms of shoshonitic (microgabbros) and alkaline (lamprophyres and diabases) geochemical affinity, which register the nature of the metasomatic lithospheric mantle under central Spain. Such magmas sometimes show a direct (or indirect) relationship with the formation of orogenic and intrusion-related gold deposits, which are relatively abundant in the Iberian Massif. The noble and base metal composition of these intrusions shows Primitive Mantle-normalized patterns characterized by positive Au and Co anomalies and fractionated platinum group elements (PGE): from lower Ir-group PGE (IPGE; Ir–Ru) to higher Pd-group PGE (PPGE; Rh–Pt–Pd). The low contents of PGE, together with the base metal contents of pyrite (which is the dominant sulphide phase in the alkaline dykes), is in accordance with low degrees of mantle partial melting and the early segregation of sulphides during magma differentiation. The scarcity of PGE mineral deposits in the Iberian Massif could be explained in part by the apparent lack of PGE enrichment in the Iberian lithospheric mantle. On the contrary, the positive Au anomaly of the SCS mafic dykes represents relatively high Au contents, similar to (and higher than) those of mafic rocks derived from metasomatized subcontinental lithospheric mantle underlying Au-endowed cratons. Several geochemical features point to subduction-related metasomatism of either oceanic or continental nature as the main source of Au enrichment. The Au re-fertilization of the lithospheric mantle under central Spain makes it a potential source in the formation of gold mineralizations.

Vaporization Modeling and Experimental Verification During Laser Beam Welding for 24Mn Steel

Vaporization modeling and experimental verification of the alloying elements that occurred during laser beam welding (LBW) of high-manganese steel were conducted. LBW using a disk laser and bead-on-plate testing was performed. Through modeling calculations at temperatures higher than 2800 K, the vapor pressure of Mn was found to be significantly larger than that of the other alloying elements. Furthermore, the vaporization flux of Mn was at least 10 times larger than that of the other alloying elements. The composition of the laser weldment was confirmed through electron probe microanalysis (EPMA), and a 1.8-wt% Mn reduction was observed in the laser weldment compared with the base metal composition. The composition of the other alloying elements, such as Fe, Cr, Si, and C, in the laser weldment was similar to that in the base metal.

Properties of welded joints of the Al – Zn – Mg – Ca alloy doped by microadditivies of zirconium and scandium

This work is devoted to the study of the structure and properties of welded joints of hot-rolled sheets from the aluminum alloy Al – 4%Zn – 2.5%Mg – 2.5%Ca – 0.2%Zr – 0.1%Sc. The joints were obtained by manual argon-arc method (TIG-welding) using a wire of own production from the base metal composition (sample AlCa) and standard welding wire Of SvAMg5 alloy (sample AlMg). It is shown that in the cast state the alloy structure consists of an aluminum solid solution (Al) (which contains 2.9% Zn, 2.5% Mg, 0.28% Zr and 0.12% Sc) and eutectic crystals of the phase (Al, Zn)4Ca with a volume fraction of ~7.6%. Microstructural investigation of wrought products showed that the formation of a structure consisting of an aluminum matrix and uniformly distributed spherical particles with a diameter of less than 2 microns occurs as a result of hot rolling with a compression ratio of 95%. The quality of welded joints produced using different additives meets the requirements for the absence of internal defects. The structure in the middle of the joints corresponds to the cast structure of the alloy and has hardness (~80 HV) inferior to the hardness (~105 HV) of the main deformed alloy. Heat-affected zone retains a relatively high hardness (at 95 HV), which is associated with a stabilizing effect of dispersed particles of the eutectic phase (Al, Zn)4Ca, and also presence of nanoparticles of the phase Al3(Zr,Sc) in the original sheet. Additional annealing of welds at 350 oC resulted in degradation of the hardness of the AlMg sample to less than 70 HV and relative cross-sectional hardness equalization in the AlCa sample to more than 90 HV. This effect can be explained by the dispersion hardening in case of the AlCa sample due to the separation of coherent nanoparticles of the Al3(Zr, Sc) phase with the L12 structure during the decay of a supersaturated aluminum solid solution. The results of mechanical tests confirmed the advantages of the strength properties of the AlCa sample over the values of the AlMg sample. All samples in the initial state and annealed sample AlMg have strength coefficients relative to the base metal from 72.4 to 75.3. The greatest mechanical properties can be achieved in the welded joint AlCa in the annealed state: UTS = 274±2 MPa, YS = 181±20 MPa, El = 2.9±0.8 %, which corresponds to a coefficient of more than 80%. This paper was prepared in the framework of the Assignment No. 11.2072.2017/4.6 for implementing a project on the following subject: Developing a process for obtaining deformed semi-finished products made of aluminium-matrix eutectic composites hardened with L12 phase nanoparticles with no quenching applied.

Variation in the Properties of Spot Weldments of Cold Rolled Mild Steel Welded with Filler Metal by Preheating

Filler metal addition has been verified as an effective way to refine mechanical behaviour of cold rolled mild steel in resistance spot welding.Negligible quantity of filler metal if added to the spot weld is found to improve mechanical properties of spot weldments , if no variation in composition of base metal and filler metal is allowed.. Looking at practical applications, sensitivity of the Resistance Spot Welding process with filler metal to variation in preheating treatment were experimentally investigated.Filler metal quantity was from 30 mg to 70 mg and preheat heat treatment was kept between 20% to 60%.The material of the filler metal is same as that of base metal and was added at the centre of overlap in lap joint.The experimentation was carried out by spot welding of specimen varying filler metal from 30 mg to 70 mg maintaining preheating cycle constant at 20%.The experimentation was then repeated for different preheat cycles.For 20% to 60% of preheat cycle, maximum breaking point was found to be varying linearly with increase in preheat level. Overall improvement in load bearing and energy absorption capability was observed as majority of specimen fail under the button pullout mode.

Effect of current and chemical composition on the hardness of weld in shielded metal arc welding

Shielded metal arc welding is the most general purpose and popular welding process. Current of welding is the main controlling factor for the properties of welded product. Hardness of the product is generally required property while in work which depends upon the chemical composition of the product. The main purpose of this research work was to investigate the effect of welding current and process of cooling on hardness and chemical composition of the weld of mild steel utilizing shielded metal arc welding process. Three pairs of mild steel plates were welded using shielded metal arc welding process at currents of 90 A, 100 A and 110 A respectively having other variables like voltage, speed of welding and feed rate etc. as constant and cooled in water of normal temperature 300 C. Similarly three other pairs of mild steel plates were welded at the said input values and cooled in normal air. The hardness values and chemical composition of base metal, heat affected zones and welded zones were recorded in all the cases and it was found that the heat affected zone has more hardness than the base metal but the weld zone has the maximum hardness. The percentage of Carbon was also found to affect the hardness of the material.

M3B2-type borides effect on the wide gap brazing of K417G alloy with mixed powder

Aerospace components are often exposed to high temperature and high pressure, which may cause relatively large wear zones. The effective repair of wide gaps is an important requirement of industrial production. In this study, a gap (width of 20 mm) was bonded by wide gap braze (WGB) technology. The Ni-based K417G alloy was used as the base metal, and a mixture of low-melting boron-containing nickel-based alloy powder and high-melting nickel-based alloy powder (similar to the base metal composition) was used as the filler material for the repair. Desired mechanical properties of the repaired joint were obtained by controlling the microstructure and the content of M3B2-type borides in the bonding layer, and by altering the size, morphology, and distribution of these boride particles. The K417G alloy repaired by sintering at 1200 °C exhibited a tensile strength of 971 MPa, completely exceeding the strength of the base metal (935 MPa). The microstructures of the joints were examined and found to include 97.56% equiaxed/spherical γ + γ′ matrix with 2.44% dispersed M3B2-type boride precipitates (∼1.4 μm). The results indicate that M3B2 boride particles mainly nucleate at the interface of γ and γ′ phases, and γ acts as the nucleation point of the high-energy grain boundary. The fine particles of M3B2-type borides are coherently precipitated in-situ in the γ phase and uniformly dispersed, facilitating excellent repair.

Welding method for high crack sensitivity of Q&T steel

Components for combat vehicles need (such as body panzers, main battle tank, armored personnel carrier) to be made of high strength and hardness steel. However, during and after the welding process is complete, this steel often leaves cracks. Quenched and Tempered Steel is made of Hot Rolled Plate Steel (thickness 8 mm), which is heat-treated with quench and temper to increase strength and hardness. The novelty of this research is the welding method to create a welded joint consisting of fine structure, high strength, and high hardness produced. This joint is produced by manual gas metal arc welding. The scheme of investigation: a) The first step. Preparation of welded specimen 120×100×8 mm in size (Fig. 3). The specimen is divided into five parts, each is given code SS (without heat treatment), S750 (heating at 750 °C), S800 (heating at 800 °C), S850 (heating at 850 °C) and S900 (heating at 900 °C). Heating rate used=10 °C/minutes. b) The second step. Heating specimen S750 at 750 °C and holding for 30 minutes, then quenching in the water medium. The same way applied to specimens S800, S850, and S900. c) The third step. The observation of metallography, hardness, and impact energy was done for SS, S750, S800, S850, and S900. d) The fourth step. Removing the first layer of the weld in half-plate thickness using a hand grinding machine of each specimen, and continue to the second layer welding. e) The fifth step. The second layer of the welds is ground in half and proceed to the final welding. f) The sixth step. Discussion of observations. g) The seventh step. Conclusions. The results of the tests carried out on KSTA 500 Steel include the chemical composition of base metal; microstructure and hardness for standard and water quenched weld joint. Medium carbon steel is equivalent to Quenched and Tempered Steel used in this study and has a high cracking susceptibility. The microstructure for the standard welded joint is dominated by martensite when quenched and tempered steel made, and martensite produced when water quenched heat treatment is conducted on the welded joint. Water quenched weld joint shows the finer microstructure of the heat-affected zone, but weld metal tends to be coarse and brittle. The highest hardness is achieved after 850 °C water quenching, i. e., base metal=578 VHN, heat affected zone=555 VHN, fusion line=457 VHN, and weld metal=252 VHN.

On the hot cracking of HSLA steel welds: Role of epitaxial growth and HAZ grain size

Centerline hot cracking is one of the major defects observed during welding of HSLA steels. While extensive efforts have been devoted to the control of weld process parameters, less attention has been paid to the influence of the starting microstructure. In the present work, the effects of the initial base metal composition and grain size, as well as of the Ni/Cu ratio of the filer metal, on the susceptibility centerline cracking, were investigated. T-type joint configuration, commonly used in the transportation and construction industries, were considered for the welding trials and the weld joints were characterized using laser confocal and electron microscopies, including chemical (EDS) and electron backscattered diffraction analysis (EBSD). Epitaxial growth was identified as the dominant solidification pattern according to thermodynamic calculations and the lattice coincidence of the δ-ferrite in HAZ and the weld metal. Results indicated that regardless of the effect of filler metal composition, hot cracking occurred at the centerline of all the more alloyed base metal welds. A correlation was established between the base metal grain size and the development and interlocking of primary and secondary dendrite arms. The grain growth kinetics of the base metals in the HAZ region was correlated to the thermal stability of microalloyed carbides and nitrides. No specific relationship between the Ni content of the filler metal and the centerline hot cracking was observed in this investigation.

Solidification Behavior of Duplex Stainless Steel (UNS S32205) Welds as a Function of WRC–1992 Diagram Equivalents and Cooling Rate

Duplex stainless steels solidify as 100 % Ferrite, however solidification of Duplex Stainless steel welds is a function of Chromium equivalent and Nickel equivalent alloying elements, filler metal and base metal composition and associated weld thermal cycle. Resultant solidification mode behavior and hence final weld metal microstructure is always a matter of interest among researcher because mechanical properties and corrosion properties are depending on weld metal ferrite content. The present research is to investigate the solidification mode behavior of duplex stainless steel welds with varying Chromium equivalent and Nickel equivalent ratios and associated weld cooling rate. In order to meet this objective, weld coupon were prepared using experimental Low Nickel, Medium Nickel and High Nickel electrodes using SMAW process, step wise increased in Nickel content from commercially available standard 09 weight percentage Nickel in E2209 design. WRC-1992 Diagram has been used to calculate Chromium Equivalent and Nickel equivalent and predict Ferrite Number using compositions of Base metal and Nickel enriched experimental electrodes. Microstructure characterization of all weld coupons is carried out using ASTM A 923 Method. Calculated values were correlated with the different microstructures developed. According to the findings of the studies, weld produced with higher Nickel content electrode, when cooled with maximum rate approximately 100.8 °C/ Sec , considered under study, exhibited FA-mode of solidification with as low as 1.71 Cr eq /Ni eq ratio and there was no noteworthy presence of intermetallic phases and precipitations in as-weld microstructures at approximate retained ferrite level of 15 Ferrite Number.

Controlled atmosphere GMAW welding of transportation vehicles and production machines parts made from 30MnB5 steel

The paper studies the influence of shielding gas on the composition and the structure of weld joint metal of 30MnB5 steel applied in essential parts of automobiles and tractors. The welding was performed in inert, oxidizing and reducing atmospheres. It was established that TIG welding with argon used as shielding gas did not provide the required mechanical properties when using conventional welding materials. Carbon dioxide during MAG welding caused partial burning of alloying elements. Carbon monoxide used as shielding gas was proved to form reducing atmosphere enabling to obtain chemical composition close to the base metal composition. Metallographic examinations were carried out. The obtained results provided full-strength weld, as well as the required reliability and durability of welded components and joints.

Mechanical and microstructure analysis of AA6061 and Ti6Al4V fiber laser butt weld

Dissimilar metal welding involves the joining of two or more different pure metals or alloys, usually by melting and mixing and often with the addition of filler metal. There are several types of dissimilar metal welds including stainless steel, either as base metal or as filler metals. Dissimilar metal joints have distinctive features because of differences in the chemical composition of base metal and filler material. Their alloying elements will diffuse intensely during welding. The structures near the fusion line are very complex. Despite of great potentiality in aircraft and automotive industries, dissimilar joining of hybrid Al-Ti structures is often challenging because of the unavoidable formation of brittle intermetallic compounds, mixing of molten phases, and significant differences in material properties. In this work, dissimilar 2mm thickness AA6000 and Ti6Al4V butt joints were produced by shifting an Yb fiber laser beam on the upper surface of the Ti sheet. Neither filler wire nor groove preparation was adopted. Different working conditions and seam shapes were assessed. The welds were characterized in terms of metallurgical and mechanical behaviors.

Comparative study of pulsed Nd:YAG laser welding of AISI 304 and AISI 316 stainless steels

Laser welding is a potentially useful technique for joining two pieces of similar or dissimilar materials with high precision. In the present work, comparative studies on laser welding of similar metal of AISI 304SS and AISI 316SS have been conducted forming butt joints. A robotic control 600W pulsed Nd:YAG laser source has been used for welding purpose. The effects of laser power, scanning speed and pulse width on the ultimate tensile strength and weld width have been investigated using the empirical models developed by RSM. The results of ANOVA indicate that the developed models predict the responses adequately within the limits of input parameters. 3-D response surface and contour plots have been developed to find out the combined effects of input parameters on responses. Furthermore, microstructural analysis as well as hardness and tensile behavior of the selected weld of 304SS and 316SS have been carried out to understand the metallurgical and mechanical behavior of the weld. The selection criteria are based on the maximum and minimum strength achieved by the respective weld. It has been observed that the current pulsation, base metal composition and variation in heat input have significant influence on controlling the microstructural constituents (i.e. phase fraction, grain size etc.). The result suggests that the low energy input pulsation generally produce fine grain structure and improved mechanical properties than the high energy input pulsation irrespective of base material composition. However, among the base materials, 304SS depict better microstructural and mechanical properties than the 316SS for a given parametric condition. Finally, desirability function analysis has been applied for multi-objective optimization for maximization of ultimate tensile strength and minimization of weld width simultaneously. Confirmatory tests have been conducted at optimum parametric conditions to validate the optimization techniques.

Low Cycle Fatigue behavior of SMAW welded Alloy28 superaustenitic stainless steel at room temperature

This paper focused on the study of Low Cycle Fatigue of welded joints of superaustenitic (Alloy28) stainless steels. Chemical composition and microstructure investigation of Base Metal (BM) and Weld Metal (WM) were identified. The results showed that both of composition is fully austenitic with a dendritic microstructure in the WM. Low cycle fatigue tests at different strain levels were performed on Base Metal (BM) and Welded Joint (WJ) specimens with a strain ratio Rε=−1. The results indicated that the fatigue life of welded joints is lower than the base metal. This is mainly due to the low ductility of the Welded Metal (WM) and the presence of welding defects. Simultaneously, Scanning Electron Microscope (SEM) observations of fractured specimens show that WJ have brittle behavior compared to BM with the presence of several welding defects especially in the crack initiation site. An estimation of the crack growth rate during LCF tests of BM and WJ was performed using distance between striations. The results showed that the crack initiation stage is shorter in the case of WJ compared to BM because of the presence of welding defects in WJ specimens.

Effect of Addition of Boron and Nitrogen on the Corrosion Resistance of Modified 9Cr-1Mo Ferritic Steel

Abstract Electrochemical noise (EN) studies were conducted on three different sets of modified 9Cr-1Mo steels containing different contents of nitrogen and boron in air-saturated 0.05 M NaCl solution at 1 Hz sampling frequency for 72 h continuously, in order to study the metastable pitting corrosion behaviour of these steels. These specimens had different combinations of boron and nitrogen (60 ppm boron and 110 ppm nitrogen, 60B + 110N), (90 ppm boron and 100 ppm nitrogen, 90B + 100N) and (100 ppm boron and 47 ppm nitrogen, 100B + 47N) respectively, while base metal composition was same. Current signal analysis was carried out to know the total number of current transients as a function of current amplitude. The statistical parameter like σI was studied to indicate the extent of localized corrosion activity. It was observed that the total number of current transients was highest for the specimen with comparable concentrations of boron and nitrogen, 90B + 100N; also it showed highest number of high current transients, suggesting its tendency towards pitting corrosion. This is mainly due to the formation of boronitrides which reduces dissolved boron and nitrogen causing increased pitting corrosion activity. Low boron (60 ppm) and high nitrogen specimen showed lowest number of high current transients, indicating improved passivation. The plots of σI as a function of time as well as cumulative probability (CP) vs. σI showed inferior pitting corrosion resistance for the former while the latter showed the least corrosion activity.

Microstructural and Mechanical Properties of 308 and 409 Stainless Steel Welded by GTAW Process

ABSTRACTToday, stainless steel is widely used in automotive industry due to its high impact resistance, corrosion resistance and light weight. This paper present the research carried out to study the differences between microstructure and mechanical properties of 409 and 308 stainless steel sheets, each joints by gas tungsten arc welding (GTAW). For each of weldments, detailed analysis was conducted on the chemical composition, microstructure characteristics and mechanical properties of base metal (BM), heat affected zone (HAZ) and fusion zone (FZ). Scanning electron microscopy (SEM) and optical microscopy were used to analyze microstructural changes and mechanical properties, including microhardness and tensile test. This study can be a practical guide in the selection of other materials in order to determine the important to use in structural automotive industry.

A química da formação do cordão na soldagem TIG

A soldagem TIG apresenta elevados níveis de estabilidade e permite um controle mais apurado do que a maioria dos demais processos de soldagem a arco. É bem conhecido, contudo, que pequenas variações de composição química do metal base ou da região de operação do arco podem ter um efeito pronunciado no formato do cordão de solda, o que reduz a capacidade de controlar e a previsibilidade do processo. Este trabalho apresenta uma revisão da variabilidade do cordão de solda obtido no processo TIG com pequenas alterações na composição química do metal base e das soldagens A-TIG e TIG com gás ativo. Aspectos comuns e particulares de cada caso são realçados e discutidos e os mecanismos propostos na literatura em cada caso são apresentados e comparados.

Catalytic and Electrocatalytic Oxidation of Ethanol over Palladium-Based Nanoalloy Catalysts

The control of the nanoscale composition and structure of alloy catalysts plays an important role in heterogeneous catalysis. This paper describes novel findings of an investigation for Pd-based nanoalloy catalysts (PdCo and PdCu) for ethanol oxidation reaction (EOR) in gas phase and alkaline electrolyte. Although the PdCo catalyst exhibits a mass activity similar to Pd, the PdCu catalyst is shown to display a much higher mass activity than Pd for the electrocatalytic EOR in alkaline electrolyte. This finding is consistent with the finding on the surface enrichment of Pd on the alloyed PdCu surface, in contrast to the surface enrichment of Co in the alloyed PdCo surface. The viability of C-C bond cleavage was also probed for the PdCu catalysts in both gas-phase and electrolyte-phase EOR. In the gas-phase reaction, although the catalytic conversion rate for CO2 product is higher over Pd than PdCu, the nanoalloy PdCu catalyst appears to suppress the formation of acetic acid, which is a significant portion of the product in the case of pure Pd catalyst. In the alkaline electrolyte, CO2 was detected from the gas phase above the electrolyte upon acid treatment following the electrolysis, along with traces of aldehyde and acetic acid. An analysis of the electrochemical properties indicates that the oxophilicity of the base metal alloyed with Pd, in addition to the surface enrichment of metals, may have played an important role in the observed difference of the catalytic and electrocatalytic activities. In comparison with Pd alloyed with Co, the results for Pd alloyed with Cu showed a more significant positive shift of the reduction potential of the oxygenated Pd species on the surface. These findings have important implications for further fine-tuning of the Pd nanoalloys in terms of base metal composition toward highly active and selective catalysts for EOR.

Optimalisasi Komposisi Kandungan MN Pada Filler untuk Mendapatkan Ketangguhan dan Kekerasan

Submerged Arc Welding (SAW) is a welding process used for fabrication of pipes, for example spiral welded pipes. The technique can be operated automatically and has a high reliability in many various welding applications. Some factors affecting the strength of weld metals are heat input, current, and chemical composition of filler, flux, and base metal. The present investigation aims to study microstructure-hardness relationship of submerged arc spiral welded steel pipes. Material used in this experiment was API 5L X-52 and API 5L X-60 for spiral welded steel pipes. Welding was carried out using voltage of 35 volt, welding speed of 13,67 mm/s whereas composition Mn on the flux was varied, 1.7; 1.4; 1.4 with Mo and 1.09. Microstructure and hardness were conducted on base metal, weld metal and heat affected zone (HAZ). Results show that, an increase in composition of Mn could be increases the amount of acicular ferrite structure in weld metal. The hardness and thougness number is increase correlated with increase number of Mn, but for the composition Mn as 1,7, the number of acicular ferrite is decrease, the consequence of hardness number is decrease.