Showing papers on "Weldability published in 2010"

Superalloys: Alloying and Performance

Abstract: This practical guide provides an introduction for understanding the compositional complexity of superalloys superalloy and the wide range of alloys developed for specific applications. The basics of alloying, strengthening mechanisms, and structure of superalloys are explained in optimizing particular mechanical properties, oxidation/corrosion resistance, and manufacturing characteristics such as castability, forgeability, and weldability.

Effects of Welding Parameters and Pre-Heating on the Friction Stir Welding of UHMW-Polyethylene

Abstract: The aim of this study was to investigate the weldability of UHMW-polyethylene via friction stir welding method. The samples were joined with single pass under 960–1960 rpm rotational speeds and 10–20 mm/min transverse speeds. In this study, three different heating processes were used. These processes are welding at room temperature, welding by pre-heating from the bottom of plastic samples at 50°C and 80°C with metal molding. A tensile test, durometer hardness test and an optical microstructure analysis were conducted on welded joint. In the experiments, a tensile strength of 72% was achieved in non-preheated welds whereas tensile strength of parent material was achieved approximately at an optimum value of 89% by pre-heating at 50°C. Pre-heating process enabled a homogeneous heat distribution by approximating the plastic material to fusing point in a short time and facilitated mixing and as a result welded joint of a supremer characteristic was obtained.

A New Paradigm for Designing High-Fracture-Energy Steels

Abstract: The steels used for structural and other applications ideally should have both high strength and high toughness. Most high-strength steels contain substantial carbon content that gives poor weldability and toughness. A theoretical study is presented that was inspired by the early work of Weertman on the effect that single or clusters of solute atoms with slightly different atom sizes have on dislocation configurations in metals. This is of particular interest for metals with high Peierls stress. Misfit centers that are coherent and coplanar in body-centered cubic (bcc) metals can provide sufficient twisting of nearby screw dislocations to reduce the Peierls stress locally and to give improved dislocation mobility and hence better toughness at low temperatures. Therefore, the theory predicts that such nanoscale misfit centers in low-carbon steels can give both precipitation hardening and improved ductility and fracture toughness. To explore the validity of this theory, we measured the Charpy impact fracture energy as a function of temperature for a series of low-carbon Cu-precipitation-strengthened steels. Results show that an addition of 0.94 to 1.49 wt pct Cu and other accompanying elements results in steels with high Charpy impact energies down to cryogenic temperatures (198 K [–75 °C]) with no distinct ductile-to-brittle transition. The addition of 0.1 wt pct Ti results in an additional increase in impact toughness, with Charpy impact fracture energies ranging from 358 J (machine limit) at 248 K (–25 °C) to almost 200 J at 198 K (–75 °C). Extending this concept of using coherent and coplanar misfit centers to decrease the Peierls stress locally to other than bcc iron-based systems suggests an intriguing possibility of developing ductile hexagonal close-packed alloys and intermetallics.

High speed friction stir welding of aluminium alloys

Abstract: In this paper, the weldability of AA 5083-H111 (non-heat treatable) and AA 6082-T6 (heat treatable) aluminium alloys, which are widely used in welding fabrication, is compared by analysing the welds obtained from both materials under a large range of welding conditions (varying tool dimensions, rotation and traverse speeds, axial loads and tilt angles) chosen to ensure high welding speeds. The differences in friction stir weldability, assessed by weld defect analysis and weld strength characterisation, will be related to the markedly different plastic behaviours of both base materials. Based on the experimental results, a methodology for determining suitable friction stir welding parameters is proposed.

Joining of molybdenum and its application

Abstract: In this work fusion and solid state welding techniques for joining PM refractory metals are adressed. The weldability is discussed and evaluated by electron beam and friction welding experiments. EB-welding experiments were performed on rolled sheets made of different Mo-based materials. While a significant decrease in the mechanical properties was found for the weldments of unalloyed molybedenum and the alloy TZM, good weldability is given for Mo41Re. A welding procedure was established and used for the manufacturing of thin walled tubes. Rotary friction welding experiments were carried out on rod material of the Mo-alloys TZM and MHC. Suitable process parameter were determined and successfully transferred for the joining of tubular TZM parts.

Effect of surface states of steel on microstructure and mechanical properties of lap joints of magnesium alloy and steel by friction stir welding

Abstract: AZ31 Mg alloy (top sheet) and steel (zinc coated steel and brushed finish steel) were friction stir lap welded, and the effect of surface states of steel on the microstructure and mechanical properties of joints was examined. The failure loads of the zinc coated steel joints could reach 2·3 kN. Mg alloy and brushed finish steel could not be welded in current experimental conditions. The presence of zinc coat promoted the formation of liquid low melting Mg–Zn eutectic products at the interface. The liquid products, as well as broken oxide films and surface contaminants, were forced out of the joining interface by the high pressure produced by the tool. As a result, fresh interfaces were exposed, which led to the mutual diffusion between magnesium alloy and steel. Findings of the present study suggest that the presence of zinc coat significantly improves the weldability in friction stir lap welding of magnesium alloy and steel.

Flux-cored wire for stainless steel arc welding

Abstract: A flux-cored wire for stainless steel arc welding including an outer sheath made of stainless steel and flux filled up in the outer sheath contains, as percentage to the total mass of the wire, Cr: 22.0-30.0 mass %, Ni: 6.0-12.0 mass %, Mo: 2.0-5.0 mass %, N: 0.20-0.35 mass %, TiO2: 4.0-9.0 mass %, SiO2: 0.1-2.0 mass %, ZrO2: 0.5-4.0 mass %, total of Li2O, Na2O and K2O: 0.50-1.50 mass %, metal fluoride in terms of fluorine amount: 0.10-0.90 mass %, and rare earth element component: 0.10-1.00 mass %, limits C to 0.04 mass % or below, W to 4.0 mass % or below, Cu to 2.0 mass % or below, Bi2O3 to 0.01 mass % or below, and limits oxides other than the above to 3.0 mass % or below. With such a composition, it is possible to obtain a weld bead which is excellent in the weldability in welding in all attitudes and is more excellent in the low temperature toughness while keeping excellent pitting corrosion resistance in arc welding of duplex stainless steel and the like.

New Method of Characterizing and Quantifying Complex Microstructures in Steels

Abstract: From the late 1960s through the late 1970s, high strength microalloyed steels hot rolled to strip and plate exhibited ferrite-pearlite microstructures with yield strengths essentially limited to the range of 350–420 MPa. However, the advent of the energy crisis of the late 1970s led to the demand for steels of higher strengths, while maintaining acceptable levels of other properties such as weldability, toughness, and formability. Since the late 1970s, it has been recognized that the strengthening mechanisms present in ferrite-pearlite steels had reached their limit in terms of grain refinement and solute and precipitation hardening; hence the barrier of 350–420 MPa was a real restraint. At about the same time, it was also recognized that higher strengths in as-processed steels could only be achieved through the use of ferrite of lower temperature formation, i.e., non-polygonal, acicular, bainitic, or martensitic ferrite, either as a monolithic matrix microstructure or as a combination. This change in ach...

Laser transmission welding of high-performance polymers and reinforced composites - a fundamental study

Abstract: This article presents investigations into the weldability of high-performance polymers and carbon fiber reinforced thermoplastics (CFRP) using laser transmission welding techniques. Fundamental studies of the absorption characteristics of CFRP as joining partner and the heat distribution within the surface due to laser impact have been performed. The welding process has been analyzed with respect to the properties of the weld seam and lap shear strength tests have been realized for different material combinations.

Flux-cored nickel-based alloy wire

Abstract: A flux-cored nickel-based alloy wire contains, based on the total mass of the wire, 3 to 11 percent by mass of TiO 2 , 0.2 to 1.3 percent by mass of SiO 2 , 1 to 3 percent by mass of ZrO 2 , and 0.3 to 1. 0 percent by mass of manganese oxides in terms of MnO 2 , contains of a total of 0.2 to 1.0 percent by mass in terms of Na, K and Li of sodium compounds, potassium compounds, and lithium compounds. The flux has a ratio ( ( [TiO 2 ] + [ZrO 2 ] ) / [SiO 2 ] ) of the total of the TiO 2 and ZrO 2 contents to the SiO 2 content of 5. 0 to 14.5, in which [TiO 2 ] , [SiO 2 ] and [ZrO 2] represent TiO 2 , SiO 2 and ZrO 2 contents. The wire shows excellent weldability in welding of all positions typically on 9% nickel steels and nickel - based alloy steels and gives a weld metal having good pitting resistance, bead appearance, and resistance to hot cracking.

Joining of Copper to Brass Using Magnetic Pulse Welding

Abstract: In magnetic pulse welding, electromagnetic pressure is used to deform, accelerate and weld workpieces. The process is mostly used for tubular specimens. In this study, experiments were performed in order to investigate the weldability of copper tubes to brass solid workpieces. The tubes had an outer diameter and wall thickness of 25,0 mm and 1,5 mm respectively. A multi-turn coil with 5 windings in combination with a field shaper was used to focus the electromagnetic flux and thus realize the high pressures needed for welding. The process parameters for joining these materials were optimised for maximum weld length. The parameters taken into account were the position of the field shaper relative to the workpieces, the width of the air gap between the tube and the internal workpiece and the energy level. The weld quality was verified based on metallographic examinations, scanning electron microscopy and hardness measurements.

Effect of Welding Speed and Defocusing Distance on the Quality of Laser Welded Ti-6Al-4V

Abstract: In this study, the weldability of 5.1-mm thick Ti-6Al-4V sheets in the mill-annealed condition was investigated using a continuous wave 4 kW Nd:YAG laser at various welding speeds and defocusing distances. The joint quality was characterized in terms of weld geometry, microstructure, defects and hardness. Although some welding defects such as underfill and porosity were observed, sound welds without cracks can be obtained using a high power Nd:YAG laser. The hardness was found to be maximum in the fusion zone (FZ) and the heataffected zone (HAZ) near the fusion boundary, beyond which a gradual decrease occurred to the base material.

Ion nitriding of a superaustenitic stainless steel: Wear and corrosion characterization

Abstract: The superiority of superaustenitic stainless steel (SASS) lies in its good weldability and great resistance to stress corrosion and pitting, because of its higher chromium, molybdenum, and nitrogen contents, when compared to general stainless steels. However, some of its applications are limited by very poor wear behavior. Plasma-nitriding is a very effective treatment for producing wear resistant and hard surface layers on stainless steels without compromising the corrosion resistance. In this work, UNS S31254 SASS samples were plasma-nitrided at three different temperatures (400, 450, and 500 °C), under a pressure of 500 Pa, for 5 h, in order to verify the influence of the temperature on the morphology, wear, and corrosion behavior of the modified surface layers. The plasma-nitrided samples were analyzed by means of optical microscopy, micro-hardness, X-ray diffraction, wear, and corrosion tests. Wear tests were conducted in a fixed ball micro-wear machine and corrosion behavior was carried out in natural sea water by means of potentiodynamic polarization curves. For the sample which was plasma-nitrided at 400 °C, only the expanded austenite phase was observed, and for the treatments performed at 450 and 500 °C, chromium nitrides (CrN and Cr2N) were formed in addition to the expanded austenite. Wear volume and Knoop surface hardness increased as the plasma-nitriding temperature increased. Higher wear rates were observed at high temperatures, probably due to the increment on layer fragility. The sample modified at 400 °C exhibited the best corrosion behavior among all the plasma-nitriding conditions.

The characteristics of high power fibre laser welding

Abstract: Laser welding has an ever growing role in manufacturing technology. Keyhole laser welding is the most important laser welding process in metal industry when exceeding the 1 mm weld penetrat...

1000MPa grade cold rolling hot dip galvanizing two-phase steel and manufacturing method thereof

Abstract: The invention provides 1,000 MPa cold-rolled hot-dip galvanized dual-phase steel and a manufacturing method thereof, belonging to the technical field of cold-rolled hot-dip galvanized high-strength steel plates. The chemical components in mass percentage of the cold-rolled hot-dip galvanized dual-phase steel are: 0.06 to 0.18 percent of C, less than or equal to 0.1 percent of Si, 1.2 to 2.5 percent of Mn,0.05 to 0.5 percent of Mo, 0.05 to 0.6 percent of Cr, 0.005 to 0.05 percent of Al, 0.01 to 0.06 percent of Nb, 0.01 to 0.05 percent of Ti, less than or equal to 0.02 percent of P, less than orequal to 0.01 percent of S, less than or equal to 0.005 percent of N, the balance being Fe and inevitable impurities. The manufacturing method adopts Cr or Mo to replace Si, so as to enlarge an austenitic and ferritic two-phase region and improve the hardenability of the dual-phase steel, and meanwhile, the manufacturing method improves the strength of toughness of the steel by adding Nb or Ti refined grains, so as to ensure that the steel has good weldability and usability, and the strength grade of the steel can reach over 1,000 Mpa.

High-performance weather-proof building structural steel and manufacturing method thereof

Abstract: The invention relates to high-performance weather-proof building structural steel and a manufacturing method thereof The composition system of low C-medium Mn-low N-micro Nb alloying-ultramicro Ti processing low content alloy weather-proof steel is taken as foundation, the acid solution Als content in the steel is increased properly, and the range of the acid solution Als content is controlled; the zero dimension Ni equivalent weight is controlled to be more than or equal to 035, the Ceq is less than or equal to 0425%, and the Mn/C is more than or equal to 10; the weather-proof property index DNH is more than or equal to 60%; and the Ca is processed, the Ca/S is controlled within the range of 10-30, and Ca*S 028 is less than or equal to 10*10 By adopting a TMCP technique, a weather-proof steel plate with good toughness, strong plasticity matching, low yield ratio, atmosphere corrosion resistance, excellent weldability and anti-fatigue performance can be obtained, is especially suitable for non-coating high-rise building structure and bridge structure, and can realize stable batch industrialized production with low cost

High strength low alloy hot rolling ferrite bainite weathering resistant steel and production method thereof

Abstract: The invention relates to a high strength low alloy hot rolling ferrite bainite weathering resistant steel and a production method thereof. The steel comprises the components by weight percent: 0.05-0.10% of C, 0.30-0.45% of Si, 1.00-1.50% of Mn, less than or equal to 0.015% of P, less than or equal to 0.01% of S, 0.50-0.70% of Cr, 0.20-0.30% of Ni, 0.20-0.40% of Cu, less than or equal to 0.05% ofAl, 0.01-0.025% of Ti, 0.03-0.05% of Nb and the rest of Fe and impurities; and the yield strength is more than or equal to 450MPa, and the welding cold crack susceptibility coefficient is less than orequal to 0.2. The invention has the advantages of low cost, high strength, low yield ratio, high weatherability, excellent weldability and low temperature toughness, simple process flow of the preparation technique and easy operation. Therefore, the invention can be widely applied to the fields such as bridges, buildings, containers, railway coaches, etc.

Evaluation of Applicability for Ni-advanced Weathering Steels and Bridge High-performance Steels to Railway Steel Bridges

Abstract: The design standard for railway steel structures and composite girders was recently revised, and its range of applicability was extended to recently developed steel materials including Ni-advanced weathering steels and Bridge High-performance Steels (BHS). Ni-advanced weathering steels can be applied without painting to bridges in corrosive environments, while BHS materials feature high strength and enhanced weldability. This paper explains the method of evaluation for the applicability of Ni-advanced weathering steels from the results of exposure tests, and outlines the advantages of BHS application to railway bridges from the results of trial design.

High strength galvanized steel sheet having excellent formability, weldability, and fatigue properties and method for manufacturing the same

Abstract: A high strength galvanized steel sheet having excellent formability, weldability, and fatigue properties and a tensile strength equal to or higher than 980 MPa and a method for manufacturing the same. The steel sheet contains all in mass%, C: 0.05% to <0.12%, Si: 0.35% to <0.80%, Mn: 2.0 to 3.5%, P: 0.001 to 0.040%, S: 0.0001 to 0.0050%, Al: 0.005 to 0.1%, N: 0.0001 to 0.0060%, Cr: 0.01% to 0.5%, Ti: 0.010 to 0.080%, Nb: 0.010 to 0.080%, and B: 0.0001 to 0.0030%, optionally one or more of Mo: 0.01 to 0.15%, Ca: 0.0001 to 0.0050%, REM: 0.0001 to 0.1%, and Sb: 0.0001 to 0.1%, and Fe and unavoidable impurities as the balance, has a microstructure containing a ferrite phase with a volume fraction in a range of 20 to 70% and an average grain diameter equal to or smaller than 5 µm, and has a galvanized layer on a surface thereof at a coating weight (per side) of 20 to 150 g/m2.

Evolution of creep resistant 316 stainless steel for sodium cooled fast reactor applications

Abstract: Sodium cooled fast reactors (SFRs) are designed to operate at high temperatures with an initial design life of about 40 years. Austenitic stainless steel (SS) types 304 and 316 and their variants have been generally used for out-of-core structural components of the reactor assembly system. The choice of these two grades of stainless steels is decided by several important factors such as high temperature mechanical properties like creep, low cycle fatigue and creep-fatigue interaction, compatibility with liquid sodium coolant, weldability, fabricability and cost. The components which operate in the creep temperature range are made of 316 SS. This material has been used extensively in the early SFRs. Studies on long term creep properties of 316 SS have clearly established the good creep resistance of this material and the microstructural stability at temperatures below 873 K. In view of the susceptibility of welded components to stress corrosion cracking, low carbon grades of 304 and 316 SS with alloying addition of nitrogen (designated as 304L(N) SS and 316L(N) SS) are used for structural components of later generation of SFRs. Nitrogen addition in the range of 0.06–0.08 wt% produces significant improvement in the creep properties of this material through solid solution strengthening and lowering of stacking fault energy. In view of the recent trends to increase the design life of SFRs to 60 years and more, it is necessary that non-replaceable structural components of reactor assembly have sufficient high temperature mechanical properties over such very long periods of operation. Increasing the nitrogen content from 0.06–0.08 wt % to levels of 0.12–0.14 wt% has been found to increase creep rupture life of 316LN SS by an order of magnitude. The beneficial effects of nitrogen are also extended to type 316 SS weld metal. This paper discusses the progressive improvements in the creep properties of 316 SS grade by varying the amounts of interstitial elements carbon and nitrogen.

High-strength cold-rolled steel sheet having elongation, stretch-flange formability and weldability

Abstract: PROBLEM TO BE SOLVED: To provide a high-strength cold-rolled steel sheet having elongation, stretch-flange formability and weldability.SOLUTION: The high-strength cold-rolled steel sheet has a componential composition comprising, by mass, 0.10 to 0.25% C, Si+Al: 0.5 to 3.0% in total, 0.5 to 3.0% Mn, <0.1% P, ≤0.005% S, ≤0.01% N, 0.10 to 0.50% V, and the balance iron with inevitable impurities, and has a structure where a soft host phase composed of tempered martensite and/or tempered bainite is comprised, in area ratio, by 20 to 60%, a hard second phase composed of retained γ and martensite is comprised by 5 to 20%, and the balance at least one selected from bainite, bainitic ferrite and austempered martensite; wherein the residual γ is comprised by ≥1% in area ratio independently. The average grain size of the hard second phase is ≤1.5 μm in terms of an equivalent circle diameter, the volume ratio of carbides with an equivalent circle diameter of 8 to 15 nm is ≥50% among carbides present in the soft host phase, and also, the number of the carbides with an equivalent circle diameter of ≥50 nm is ≤3 pieces per 1 μmof the soft host phase.

Spot weldability of δ-TRIP steel containing 0·4 wt-%C

Abstract: Strong steels are usually difficult to resistance spot weld because of the tendency to form hard phases. This applies particularly to the transformation induced plasticity (TRIP) assisted steels with relatively high carbon equivalents. A new development in this context is the δ-TRIP steel, designed to retain δ-ferrite as a stable phase at all temperatures below melting. Fully martensitic regions are therefore avoided, making it possible to weld in spite of the high carbon concentration. The authors present here the first spot welding tests on the novel alloy system.