Showing papers on "Weldability published in 2005"

Welding Metallurgy and Weldability of Stainless Steels

Abstract: Preface 1 Introduction 2 Phase Diagrams 3 Alloying Elements and Constitution Diagrams 4 Martensitic Stainless Steels 5 Ferritic Stainless Steels 6 Austenitic Stainless Steels 7 Duplex Stainless Steels 8 Precipitation-Hardening Stainless Steels 9 Dissimilar Welding of Stainless Steels 10 Weldability Testing Appendix 1: Nominal Compositions of Stainless Steels Appendix 2: Etching Techniques for Stainless Steel Welds Author Index Subject Index

High-strength steel development for pipelines: A brazilian perspective

Abstract: The production of American Petroleum Institute (API) class steels using the traditional controlled rolling route rather than the process involving accelerated cooling necessitates a careful adjustment of steel composition associated with the optimization of the rolling schedule for the deformation and phase transformation characteristics of these modified alloys. The current work presents a study of two, NbCr and NbCrMo, steel systems. The microstructure obtained is correlated not only with the resulting mechanical properties, but also with the weldability and resistance to damage in the aggressive environments to which the materials are exposed. The evaluation of the steels was undertaken at two stages along the production route, sampling the material as plate and as tubular product, according to the API 5L 2000 standard. Tensile testing, Charpy-V impact testing, and hardness measurements were used to determine the mechanical properties, and microstructural characterization was performed by optical and scanning electron microscopy. The results showed that it was possible to obtain good impact properties, for both steels, in plate and tube formats. The Charpy-V impact energy, measured at −20 °C from 100 to 250 J corresponds to a toughness level above that required by the API 5L 2000 standard, which specifies 68 to 101 J at 0 °C. The yield strength (YS) to ultimate tensile strength (UTS) ratio was determined to be 0.8, the API standard establishing a maximum limit of 0.93. Both of the alloys investigated exhibited a bainitic microstructure and were successfully processed to fabricate tubular products by the “UOE” (bending in “U”, closing in “O,” and expanding “E”) route. with regard to weldability, the two experimental steels exhibited a heat-affected zone (HAZ) for which toughness levels (using the temperature associated with a 100 J impact energy as a base for comparison) were higher than those for both the base metal (BM) and the weld metal (WM) itself. In order to perform the evaluation of the behavior of the steels in an aggressive environment, more specifically their resistance to the deleterious effects of H2S, slow strain rate tests (SSRTs) were carried out, immersing the samples in a sodium thiosulfate solution during the tests. Though no secondary cracking was observed in the test samples, the ductility levels measured were lower than those for the same materials tested in air. Constant load tests were also conducted according to the standard NACE conditions. Despite the more aggressive nature of the test solution in these cases, no samples of either steel suffered failure.

Ultra High Strength FeMn TWIP Steels for automotive safety parts

Abstract: Energy savings are among the most important goals of steel users. But generally, the increase of Tensile Strength for a given metallurgy is obtained to the detriment of ductility. Arcelor develops new ultra high strength steel with TWinning Induced Plasticity (TWIP) effect for weight reduction and impact resistance. This product, based on manganese (Mn) alloying metallurgy, has a tensile stress higher than 1000 MPa for a total elongation superior to 50%. Mechanical properties of these new steel grades are reported, in terms of tensile and forming behaviour, weldability and fatigue. Optimised designs are presented for safety parts in FeMn TWIP 1000 and assessed against conventional UHS steel. Tensile and formability properties are presented first by means of basic tests (stretching, bending, etc.) in order to classify the different steels. Crash resistance is investigated by using a dynamic axial compression test and a dynamic three point bending test on structural components with closed and open cross sections. For each steel grade, the estimated weight saving potential is compared with respect to parts manufactured in high drawing ability steel. The exceptional mechanical characteristics of this product permit to propose innovative steel design solutions for automotive safety component.

Development of New Low Transformation-Temperature Welding Consumable to Prevent Cold Cracking in High Strength Steel Welds

Abstract: There has been growing interest in high strength steel with a tensile strength higher than 800 MPa, which would be ideal for weight reduction and better performance of steel structures. However, there are two major problems in the application of high strength steel to structures. One is that the fatigue strength of welded joints is far lower than that of the base metal, and the other is that the weld metal and the heat-affected zone (HAZ) are likely to have cold cracking. These problems must be solved before high strength steel can be widely used in steel structures. As a solution to the problem of cold cracking, a reduced preheating type of high strength steel has recently been developed in which cold cracking in the HAZ is reduced by reduction of alloy components (lower Ceq, Pcm) without loss of strength. However, since the resistance to cold cracking of the weld metal has not been improved, preheating of the weld metal is still necessary, and the problem remains toward its wider use. Recently, Ohta et al. developed a low transformation-temperature welding consumable, in which compressive residual stress is induced by transformation expansion of martensitic transformation of weld metal at a low temperature near room temperature, and demonstrated that this consumable improves the fatigue strength of welded joints. We considered that the reduction of tensile residual stress in the low transformation-temperature welding consumable might also be effective in decreasing the cold cracking and that this consumable would be useful in manufacturing high performance welded joints with improved fatigue strength and cold-cracking resistance. In the present study, we examined the effects of low temperature-transformation weld materials on the prevention of cold cracking in high strength steel. Firstly, the y-shaped weld cracking tests demonstrated that reduction of residual tensile stress induced by martensitic transformation expansion of weld metal was effective in reducing cold cracking. Secondly, the effects of the degree of joint constraint on cold cracking in low transformation-temperature weld materials were examined by the y-shaped and H-shaped weld cracking tests. The cracking ratio was high at low degrees of joint constraint and low at high degrees of joint constraint. Two causes were considered: one was that the reduction of tensile residual stress by transformation expansion is higher at a higher degree of joint constraint, and the other was that the weld metal of martensitic structure alone is sensitive to cold cracking. According to the above investigation, we attempted to develop a weld material with high resistance to cold cracking at different degrees of constraint. To maintain the effects of reduction of tensile residual stress by transformation expansion to reduce the amount of diffusible hydrogen and the sensitivity of cracking, which are other causes of cracking, we designed and developed a 2-microstructure phase weld metal (martensite + retained austenite) by modifying the low temperature-transformation weld material to obtain a lower Ms point. We examined the effects of the degree of joint constraint on cold cracking, and confirmed that the cracking rate of the modified rod was almost 0% at all degrees of constraint, and its resistance to cold cracking was high.

New Generation 21/4Cr Steels T/P 23 and T/P 24 Weldability and High Temperature Properties

Abstract: Creep resistant steels for high temperature service are a vital part in the construction of power stations. The possibilities to increase steam parameters of new boilers are restricted if pressure and temperature in the membrane water-walls cannot be simultaneously increased. The increase of steam parameters requires the development of new high strength and creep resistant materials. This paper gives data on weldability, mechanical properties, toughness and high temperature behaviour (creep) of new materials T/P 24 (7CrMoVTiB10-10) which have been developed by Vallourec & Mannesmann Tubes, and T/P 23 (7CrWVMoNb9–6). It is the outcome of a research project of the Belgian Welding Institute in collaboration with Laborelec and with industrial partners. Both base metals and weldments in tubes and thick walled pipes have been investigated.

HIGH-Mn STEEL MATERIAL AND MANUFACTURING METHOD THEREFOR

Abstract: PROBLEM TO BE SOLVED: To provide a high-Mn steel material superior in characteristics not only of low-temperature toughness and weldability but also of a coefficient of thermal expansion, permeability and heat conductivity. SOLUTION: The high-Mn steel material has a chemical composition comprising, by mass%, 0.01-0.25% C, 0.01-0.5% Si, 15% to 40% Mn, 0.5% to COPYRIGHT: (C)2007,JPO&INPIT

Thermomechanically Hot Rolled High and Ultra High Strength Steel Grades - Processing, Properties and Application

Abstract: In all application fields for hot rolled strip products for direct processing, e.g. construction and engineering but also crane and truck industry, there is a strong customers demand for grades with increased strength levels and well balanced formability. At voestalpine Stahl GmbH these requirements were met with the development of the high strength microalloyed steel grade ALFORM700M and the ultra high strength steel grade ALFORM900M with a minimum yield strength (YS) of 700 MPa and 900 MPa, respectively. In the present paper investigations on the steel grades ALFORM700M and ALFORM900M are introduced. To explain the evolution of the obtained complex microstructures consisting of bainitic ferrite, bainite and martensite alloy design and industrial production process is discussed on the base of dilatometric experiments and TEM investigations. The formation of precipitates is studied by using a numerical model, chemical methods and mechanical testing after heat treatment. Mechanical and mechanic-technological properties of the two steel grades are compared. Furthermore, some processing aspects as weldability an bending behaviour are highlighted. Finally, some typical applications for this high and ultra high strength steel grades are presented.

Metals Affordability Initiative: Application of Allvac Alloy 718Plus® for Aircraft Engine Static Structural Components

Abstract: Mechanical property balance, malleability, and weldability of Alloy 718 have driven widespread utilization across the aerospace and non-aerospace industries for nearly 50 years. However, the metastability of the primary strengthening gamma double prime phase is typically unacceptable for applications above about 650°C. As a result, other more costly and difficult to process alloys, like Waspaloy, are used in such applications. The latter alloys, strengthened primarily by gamma prime, are also more sensitive to weld-related cracking than Alloy 718. As part of the Metals Affordability Initiative CORE Program, several alternate alloys were identified and evaluated for aircraft engine static structural component applications for use temperatures of at least 700°C. The application-integrated project team consisting of engine manufacturers, General Electric, Honeywell, and Pratt & Whitney; forgers Firth-Rixson and Ladish Co., Inc.; primary metal producers, Allvac and Carpenter Technology; and the Air Force Research Laboratory, selected the Allvac-developed 718Plus® alloy composition for scale-up and validation. Subscale and full-scale experiments confirmed that processability and weldability of this alloy were significantly improved relative to Waspaloy, approaching that of Alloy 718. Complex rolled rings varying in size from less than 25 to nearly 250 kg have been processed validating the advantages of this alloy. Assessment suggests capability similar to Waspaloy to 704°C has been achieved along with an acceptable balance of other properties. This paper will summarize the processing, weldability, and mechanical property evaluations successfully performed in this project, as well as progress toward industrial implementation of this alloy.

Easy cut by flame abrasion-resistant steel in high rigidity, in toughness and preparation method

Abstract: A high-hardness and-toughness antiwear steel plate easy to be cut by flame proportionally contains Fe, C, Si, Mn, Nb, Ti, B, Cr and additive element chosen from Ni, Mo, 'Al, Cu, V, Ca, REM and Mg. Its preparing process includes rolling and quenching from the temp not lower than Ar3 conversion point to the temp lower than M2 conversion point. It has better weldability.

Recent Developments in Weldability Testing

Abstract: The term "weldability" can be used to describe a wide variety of material characteristics when a material is subjected to welding. These may include the physical and mechanical properties of the material, the ease with which welding can be accomplished from a practitioner's standpoint, or the ability of the material to avoid metallurgical degradation, usually assessed by its susceptibility to cracking during welding or subsequent heat treatment. A number of weldability tests have been developed over the years to evaluate and quantify material weldability. Many of these test techniques have focused on the phenomenon known as "hot cracking". This paper will review the basic concepts associated with hot cracking and other forms of elevated temperature cracking associated with welds and describe some recent advances in the use of testing approaches to quantify susceptibility to these forms of cracking. This description will include the use of the Varestraint test, the cast pin tear test, and the Gleeble1 thermo-mechanical simulator for quantifying cracking susceptibility and providing comparative measures of weldability among alloys.

Influence of scandium on weldability of 7010 aluminium alloy

Abstract: The commercial 7000 series aluminium alloys are based on medium strength Al–Zn–Mg and high strength Al–Zn–Mg–Cu systems. The medium strength alloys are weldable, whereas the high strength alloys are non-weldable. This is because the amount of copper present in these alloys gives rise to hot cracking during solidification of welds. As a result, the high strength Al–Zn–Mg– Cu base alloys are not used for applications where joining of components by welding is an essential step. In the present study, using a combination of qualitative Houldcroft test and quantitative Varestraint test, it is shown that a small addition of scandium to the commercial 7010 alloy reduces the hot cracking susceptibility during solidification of welds produced by the gas tungsten arc welding process. The improvement in weldability is found to be the result of the considerable grain refinement in the weld structure following the scandium addition. The results of microhardness and tensile tests are further described within the...

The effect of alloying on the resistance of carbon steel for oilfield applications to CO2 corrosion

Abstract: A systematic study has been conducted to investigate the influence of a wide range of alloying elements and different processing conditions on the resistance of low-carbon steels to CO2 corrosion. Strong carbide-forming microalloying elements such as Ti, Nb and V, along with Cr additions, and different levels of Mn, Si, Cu, Mo and Ni, have been explored, along with treatments simulating different processing conditions, for example, controlled rolling, and quenching and tempering. Corrosion testing, including flow loop tests, has been carried out, along with evaluation of mechanical properties, weldability and hot ductility. The programme has developed steels with improved CO2 corrosion resistance and hence identified a potential route for producing more economical carbon steels for oilfield applications. The work has been carried out as part of the UK- Brazil Corrosion Network.

Recent Developments in Weldability Testing for Advanced Materials

Abstract: The term “weldability” has been used to describe a wide variety of characteristics when a material is subjected to welding. These include the physical and mechanical properties of the welded structure, the ease with which welding can be accomplished from a practitioner’s standpoint, the ability of the material to avoid metallurgical degradation (usually assessed by its susceptibility to cracking during welding or subsequent heat treatment), and the ability of the welded structure to perform in its intended service environment. A number of weldability tests have been developed over the years to evaluate and quantify material weldability. Many of these test techniques have focused on the phenomenon known as “hot cracking”. This paper will review the basic concepts associated with hot cracking and other forms of elevated temperature cracking and describe some recent advances in the use of testing approaches to quantify susceptibility to these forms of cracking. This description will include the use of the Varestraint test, the cast pin tear test, and the Gleeblei thermo-mechanical simulator for quantifying cracking susceptibility and providing comparative measures of weldability among alloys.

High tensile galvannealed steel sheet having excellent workability and molten metal embrittlement crack reistance

Abstract: PROBLEM TO BE SOLVED: To provide a high tensile galvannealed steel sheet which exhibits a high tensile force of ≥580 Mpa, is improved in molten metal embrittlement resistance during spot welding, and is excellent in weldability and workability. SOLUTION: The composition of the base steel (each by mass%) of the steel sheet comprises 0.04 to 0.25% C, 0.01 to 2.0% Si, 0.5 to 3.0% Mn, ≤0.1% P, ≤0.03% S, further one or two or more kinds of 0.001 to 0.1% Ti, 0.001 to 0.1% Nb, 0.01 to 0.3% V, 0.01 to 0.5% Mo, 0.01 to 0.5% Zr, comprises, as necessary, 0.0001 to 0.01% B, wherein the metal structure comprises one or two or more kinds of a ferrite phase, bainite phase, pearlite phase and martensite phase of 40 to 95% in area rate, and the balance 1 to 10% volume fraction residual austenite phase. The metal structure is preferably dispersed with the deposited material or compound deposited material of Ti, Nb, V, Mo, and Zr of 3 to 200 nm in average grain size. COPYRIGHT: (C)2007,JPO&INPIT

High-strength hot-dip galvanized steel sheet with excellent spot weldability and stability of material properties

Abstract: A high-strength hot-dip galvanized steel sheet is provided which comprises a composite structure consisting essentially of ferrite and martensite. The steel comprises, by mass %, C: 0.05 to 0.12%, Si: not more than 0.05%, Mn: 2.7 to 3.5%, Cr: 0.2 to 0.5%, Mo: 0.2 to 0.5%, Al: not more than 0.10%, P: not more than 0.03%, and S: not more than 0.03%. The high-strength hot-dip galvanized steel sheet has not only excellent spot weldability, but also excellent “stability of material properties”, including tensile strength, total elongation, and yield strength, in a high range of strengths from 780 to 1180 MPa, even if the manufacturing condition (especially, the condition of the cooling process after annealing the steel sheet) is changed.

New generation creep-resistant steels, their weldability and properties of welded joints: T/P92 steel

Abstract: One of the important materials used in the building of modern power units is T/P92 steel, developed in Japan in 1990, and also known as NF 616. In comparison with P91 steel, this alloy contains some tungsten (up to 2%), less molybdenum (at 20.6%) and microscopic traces of boron. At the temperature of 600 °C, its resistance to creep is about 30% higher. The main application for small diameter, thin walled tubing made of T92 steel is found in super heaters, and secondary super heaters in the power stations operating at supercritical parameters. The thick walled large diameter piping in P92 steel is used for fresh and superheated steam in the chambers and pipelines that work at extreme temperatures and pressure (Table 1).

Acicular constituent high strength weathering resistant steel and producing method thereof

Abstract: The present invention relates to high strength high weather resistance steel with needle structure and its production process, and belongs to the field of low alloy steel making The present invention adopts very low carbon content to result in normal temperature dissolvability in alpha-Fe not higher than 00218 wt%, adds Cu, Cr, Ni, Mo, Nb, Ti, Al, Zr, RE and Ca, and ensures the main structure is needle-like structure for excellent weather resistance The steel of the present invention is produced by means of hot rolling technology and relaxation-separation control technology and has low production cost and short production period It has excellent weather resistance, excellent toughness, and excellent weldability needing no preheating before welding and heat treatment after welding, and may be used widely in bridge, building, traffic facility, sea platform, etc

Weldability of alloys with directionally-solidified grain structure

Abstract: A method of welding alloys having directionally-solidified grain structure. The methods improve the weldability of these alloys by creating a localized region of fine grain structure, wherein the welding occurs in these localized regions. The localized regions are formed by applying strain energy using a variety of different methods, such as by hammer peening, laser peening or sand blasting. Then, a heat treatment step may be used to create recrystallized grains having the fine grain structure. The region of fine grain structure provides better weldability.

Experimental investigation on the weldability and forming behavior of aluminum alloy tailor-welded blanks

Abstract: Aluminum alloy tailor-welded blanks (TWBs) have developed rapidly due to increasing interest and market pressure [J. M. Story, S. Heinemann, and S. Naegeler, Light Metal Age 56, 40–47 (1998). R. W. Davies, H. E. Oliver, M. T. Smith, and G. J. Grant, J. Minerals, Metals Mater. Soc. 51, 46–50 (1999)] from the automotive industry to further reduce the weight and cost of automotive components. In this study, a 5754-O aluminum alloy with a thickness of 1 mm was laser-welded by a 2 kW Nd: yttritium–aluminum–garnet (YAG) laser to produce a total of approximately 120 samples of TWBs with a similar thickness combination of 1 mm/1 mm. From the knowledge of the weld surfaces, weld profiles and tensile properties of the specimens of TWBs, the optimal welding parameters were identified and used to produce TWBs of varying widths and welding orientations for the Swift forming test. Thus, it was possible to measure and analyze the forming behavior, including the failure mode and the forming limit diagram (FLD), of the TW...

Steel plate excellent in machinability, toughness and weldability, and method for production thereof

Abstract: A steel plate which has a thickness of 4 mm or more and less than 10 mm, wherein interior portions thereof having distances from its surface of 1/4 and 3/4 of its thickness have a ferrite proportion of 30 to 90 %, and an interior portion having a distance from the surface thereof of 1/2 of its thickness has a ferrite proportion of 20 to 90 %; and a steel plate which has a thickness of 10 to 100 mm, wherein interior portions thereof having distances from the surface and the back surface thereof of 2 mm have a ferrite proportion of 30 to 90 %, and interior portions thereof having distances from its surface of 1/4, 1/2 and 3/4 of its thickness have a ferrite proportion of 20 to 90 %. The above steel plate is produced by a method comprising using a steel having the contents of C, Si, Mn, P, S, Al and N being limited to prescribed ranges and optionally further containing Mo, Cr, Nb, Ti, V, Cu, Ni, B, REM, Ca, Zr and/or Mg, and strictly specifying the balance between components of the steel, and comprising strictly controlling the conditions in rolling, washing with water, and the like, and is excellent in machinability, toughness and weldability.

Laser beam welding of titanium nitride coated titanium using pulse-shaping

Abstract: A new welding method which allows the assembly of two titanium nitride coated titanium parts is proposed. The welding procedure utilizes the possibility for pulse-shaping in order to change the energy distribution profile during the laser pulse. The pulse-shaping is composed of three elements: a) a short high power pulse for partial ablation at the surface; b) a long pulse for thermal penetration; and c) a quenching slope for enhanced weldability. The combination of these three elements produces crack-free welds. The weld microstructure is changed in comparison to normal welding, i.e. with a rectangular pulse, as the nitrogen and the microhardness are more homogenously distributed in the weld under pulse-shaping conditions. This laser pulse dissolves the TiN layer and allows nitrogen to diffuse into the melt pool, also contributing to an enhanced weldability by providing suitable thermal conditions.

Low carbon niobium alloyed high strength steel for automotive hot strip

Abstract: Hot rolled strip from microalloyed high strength steel typically has a carbon content up to 0·12% A carbon content close to the peritectic range enhances the susceptibility to surface defects such as edge and transverse cracks, which have to be removed by, for example, scarfing and grinding before hot rolling These defects can be avoided when a low carbon content is applied It has been demonstrated that by reducing the carbon content in linepipe steel to ∼003%, further improvements in toughness, ductility and weldability are achieved Furthermore, a low carbon content promotes niobium carbide solution during reheating of the slab before hot rolling This permits the application of higher niobium contents than are usually applied Niobium contents up to 010% have recently been adopted in low carbon pipe steel Besides refining the grain size during austenite processing, niobium in solid solution leads to an additional strength increase by delaying the γ→α transformation, thus promoting a high

Effect of weld metal copper content on HAZ cracking in austenitic stainless steel welded with Al brass

Abstract: Austenitic stainless steel has good weldability but is sensitive to hot cracking such as solidification and liquation cracking. In the present study, specimens of dissimilar metals made from austenitic stainless steel and Al brass were welded by the GTAW process using four different filler metals. Cracks were detected in the heat affected zone of the stainless steel when welded with CuAl, CuSn and NiCu filler metals, but no cracks were detected when a Ni filler metal was used. The cracks propagated along the grain boundary in the heat affected zone near the fusion line to the base metal of 316L stainless steel. The cracks were located inside the weld bead with very fine hairline cracking. All cracks initiated at the fusion line and moved forward in the base metal. From energy dispersion spectroscopy (EDS), the Cu peak was detected only in the crack-opening area.

Anti-corrosion and/or anti-scaling coating for metals (especially steel) is applied by wet methods and heat treated to give a weldable coating

Abstract: An anti-corrosion and/or -scaling coating for metals (especially steel) has the following characteristics : (1) it is provided with an agent for achieving (especially point) weldability of the coating; (2) it is applicable by a wet method; (3) it has its structure altered by heat processing at above 600[deg]C; and (4) it is suitable as an undercoat or primer for further coatings.

Steel for welded structure excellent in low temperature toughness of heat affected zone of welded part, and method for production thereof

Abstract: A steel for a welded structure excellent in low temperature toughness of a heat affected zone, characterized in that it is produced by a method which comprises providing a molten steel containing, in mass %, 0.03 to 0.12 % of C, 0.05 to 0.30 % of Si, 1.2 to 3.0 % of Mn, 0.015 % or less of P, 0.001 to 0.15 % or S, 0.10 % or less of Cu + Ni, 0.001 to 0.050 % of Al, 0.005 to 0.030 % of Ti, 0.005 to 0.10 % of Nb and 0.0025 to 0.0060 % of N, casting the molten steel by a continuous casting method with a cooling speed in the secondary cooling from a temperature near the solidification point to 800˚C of 0.06 to 0.6˚C/s, to prepare a cast material, subjecting the cast material to hot rolling and cooling the rolled material from a temperature of 800˚C or higher; and a method for producing the above steel for a welded structure. The above steel allows the production of a high strength thick steel plate for a marine structure excellent in weldability and in the low temperature toughness of HAZ, and can be produced at a low cost without the use of a complicated production method.

Resin coated metal plate having excellent formability, weldability and corrosion resistance, and worked articles using the resin coated metal plate and method for manufacturing same

Abstract: A resin coated metal plate having excellent formability comprises, on a metal plate, a resin coating layer containing a conductive filler and a corrosion inhibitor, a matrix resin constituting the resin coating layer is made mainly of a flexible epoxy resin and has a modulus of elasticity of not less than 3 GPa. When secondarily cured, the resin coated metal plate is imparted with excellent weldability and corrosion resistance.