Extra High Strength Research Articles

White paper: Achieving high hoop strength for composite profiles using pull-winding

In straight tubes, any force applied to the cylindrical wall causes hoop stress. Tool handles, a mop handle for example, experience hoop stress when being used actively or roughly handled. To ensure composite tubes can meet these challenges, the profiles must be manufactured with cross-aligned fibers, providing extra stiffness and high mechanical strength in transverse direction. Here Lauri Turunen, product business owner for tubes, tool handles and telescoping poles and pull-winding expert at Exel Composites, compares different manufacturing techniques and explores how the continuous manufacturing technology of pull-winding can achieve high hoop strength.

Enhanced Mechanical Properties of a Low‐Carbon Martensitic Steel by Thermally Stable Ni‐Rich Austenite

A multistep quench−lamellarization−tempering treatment (QLT) is designed for a low‐carbon high‐Ni martensitic steel to obtain extra high strength, low yield‐to‐tensile ratio, and extra high cryogenic toughness. A mixed microstructure composed of intercritical ferrite, tempered martensite, and Ni‐rich retained austenite (RA) is obtained under the QLT treatment process. The volume fraction of Ni‐rich RA is 13.6% in the QL655T sample. The QL655T sample has a yield strength of 915 MPa and tensile strength of 1080 MPa, leading to a lower yield‐to‐tensile ratio of 0.85. In addition, a total elongation to failure of 19.9% and Charpy impact toughness of 190 J at −196 °C are encouraging in comparison with the conventional counterparts. During tensile deforming, the blocky RA grains can transform easily with increasing strain, while the strain leads to rotations of the film‐like RA grains before the transformation. The RA grains with high thermal stability are attributed to the enrichment of Ni and the effect of size, which makes the ≈11.6% RA grains remain at −196 °C in the QL655T sample. During impact, the transformation‐induced plasticity (TRIP) effect of RA leads to the excellent cryogenic toughness of the QL655T sample.

A Novel Plate-Based System (UNIMAX) for Posterior Instrumented Spinal Fusion.

IntroductionThe polyaxial head pedicle screw-rod system is a commonly used spinal instrumentation technique to achieve stabilization, deformity correction, and bony fusion. We present a novel plate-based pedicle screw system (UNIMAXTM) that can be used for multi-level instrumentation with potential advantages for selected applications.MethodsBilateral titanium monoaxial pedicle screws are linked at each level by robust transversely oriented cross plates forming ring constructs capable of rigid triangulation at each level. The cross plates are then interconnected by sagittally oriented rigid plates situated medial to the screw heads. Biomechanically, the construct was tested for quasi-static torsion and fatigue in axial compression. The system is approved by the Food and Drug Administration (FDA). The system and case examples are presented showing its potential advantages.ResultsThe quasi-static torsion, the mean for the angular displacement, torsional stiffness, and torsional ultimate strength was 2.5 degrees (SD ± 0.8), 5.3 N-m/mm (SD ± 0.7), and 21.6 N-m (SD ± 4.4). For the fatigue in axial compression, the closed ring construct failed when the applied load and bending moment were ≥ 1500 N and ≥ 60 N.m. This system maximizes the construct rigidity, allows easy extension to adjacent levels, and can be incorporated intuitively into practice. The ring construct with triangulation at each level, together with its biomechanical robustness, predicts a high pullout resistance. It requires an open posterior approach incompatible with minimally invasive techniques.ConclusionThis system may have advantages over the screw-rod systems in carefully selected situations requiring extra rigidity and high pull-out strength for complex reconstructions, sagittal and/or coronal correction, patients with poor bone quality, revisions, and/or extension to adjacent levels.

Verification of Friction Models Implemented in the Simulation Software

Modern approaches in simulations of sheet metal stamping processes are based on definition the friction coefficient as not constant, but the different value in different regions, considering the nature of the actual deformation process in each individual region. In this contribution the regression and analytical models to determine the friction coefficients under blankholder and on the die drawing edge by strip drawing test are presented. These models were verified by experimental strip drawing test under the same contact conditions. Zn coated steel sheets for the automotive industry were used in experiments and simulations – extra deep drawing quality DX54D and high strength steel TRIP. The results indicate, that friction coefficients are not constant and depend on the pressure on the die contact surfaces. Friction coefficients were determined also at the cup test by the regression model of drawing versus blankholding force. Conformity of friction coefficients obtained by the cup and the strip tests was confirmed. Model of friction applied in FEM simulation was verified by cup test and good conformity was found out.

Three Generations Micro-Allying Steel Processing: Thirty Years of Successive Work at CMRDI

The present article presents cumulative works, which were carried out in the field of micro-alloying steel processing at Central Metallurgical R&D Institute (CMRDI) and/or full scale trials in collaboration with the Egyptian steel industry.It was agreed upon defining three main generations of processing micro-alloying steel. The 1stgeneration starts officially on 1975 and continues up to 1995, where it deals with using Ti and V as micro-alloying elements for steel long products. On the year 1985, Central Metallurgical R&D Institute (CMRDI) succeeded to implement of HSLA V-micro-alloyed rebar steel grades at Delta steel mills instead of conventional rebar grades.The 2nd generation was starting on late 1995 and continued to 2005. It was dealing mainly with low carbon content steel (0.04-0.08 %) for flat products (plate and sheet). The most successfully used micro-alloying element was Nb. Beside its precipitate forming effect, Nb is working as substitution solid solution strengthener. Moreover, it raises the recrystallization temperature (Tr). Mainly, micro-alloyed flat steels were developed to fulfill the requirements of the American Petroleum Institute (API) specifications 5L- Product Specification Levels (PSL1) and (PSL2) for manufacturing oil and natural gas pipelines. Meanwhile, a newly born Compact Slab Processing (CSP)-hot strip direct rolling technology was created. On years 2002, the metal forming department in CMRDI succeeded to implement controlled rolling of hot strip Nb-steel sheet at the Compact Slab Process (CSP) Machine in Alexandria National Iron and Steel (ANSDK) Company. Controlled hot rolling schedules were used and followed by early and late cooling at the run out table (ROT). Both contracts were fruitfully succeeded to introduce the API X52 grade at ANSDK Company, followed by X60, and X70 steel grades at Ezz Flat Steel (EFS) Company. The essential mechanical properties of the processed API steel sheets were matched with the API 5L-PSL2 specifications.The 3rd generation was initially developed after 2005 and continued up to day. It deals with micro-alloying with special functional elements like Boron (B). Boron was favored as a micro-alloying element for bilateral effects. Boron carbide (B4C) precipitates are the hardest after diamond, which would be reflected on raising the mechanical properties of the steel. Moreover, Boron was favorably used because it delays the temper embrittlement phenomena. On year 2014, the National for Military Industrialization authority requested from CMRDI to collaborate with Military Factory 100 to develop a technology package for processing armor steel plates. Trials were started with a 3rd generation B-micro-alloyed steel alloy. Many other alloying elements were used beside Boron to develop extra high strength 6.0 mm thickness plates. Finish hot rolled plates were then subjected to a subsequent water quenching from 900 °C and followed by tempering at 250 °C for 20 min. Representation 50X50 cm2 steel plates were successfully passed after 3 bullets in front and 3 bullets rear shooting.

A new 2.4 GPa extra-high strength steel with good ductility and high toughness designed by synergistic strengthening of nano-particles and high-density dislocations

A new 0.25C2Cr10Ni8Co2Mo2Al steel was designed and fabricated by vacuum induction melting, forging and heat treatments. Excellent mechanical properties with a combination of a 2.4 GPa ultimate tensile strength, a 2.1 GPa yield strength, a 11.4% total elongation and a 37 J/cm2 V-notch impact toughness were obtained. Such a combination of strength–ductility–toughness of the present steel is much superior than any reported conventional ultrahigh strength steel. The excellent mechanical properties of the steel can be well interpreted by synergistic strengthening of high-density dislocations, strong segregations of C, Mo and Cr on dislocations and massive nanosized NiAl precipitations.

A New 2.4gpa Extra-High Strength Steel with Good Ductility and High Toughness Designed by Synergistic Strengthening

A new 0.25C2Cr10Ni8Co2Mo2Al steel was designed and fabricated by vacuum induction melting, forging and heat treatments. Excellent mechanical properties with a combination of a 2.4 GPa ultimate tensile strength, a 2.1 GPa yield strength, a 11.4% total elongation and a 60 J/cm2 U-notch impact toughness were obtained. Such a combination of strength-ductility-toughness of the present steel is much superior than any reported conventional ultrahigh strength steel. The excellent mechanical properties of the steel can be well interpreted by synergistic strengthening of high density dislocations, strong segregations of C, Mo and Cr in dislocations and massive nanosized NiAl precipitations.

Formability Investigations of Advanced High Strength Steels

Car manufacturing has been significantly influenced by sheet metal forming developments, thus the requirements and developments in car manufacturing have decisive role in the development of sheet metal forming, too. The automotive industry is facing challenges of reducing body weight in consideration of environmental problems and higher collision safety. These requirements are being addressed by the application of various dual-phase steels, ultra and extra advanced high strength steels (UHSS, XAHSS). Forming Limit Diagrams (FLD) are the most appropriate tools to characterize the formability of sheet metals. Theoretical and experimental investigations of forming limit diagrams are in the forefront of todays’ research activities. In this paper, an up-to-date research methodology elaborated and applied at the Department of Mechanical Technology at the University of Miskolc will be shown.

The effect of low stress triaxialities and deformation paths on ductile fracture simulations of large shell structures

In accidental limit state analysis of ship structures and their components, the common assumption is that failure takes place in the plate field under multi-axial tension, thus most advancements in developing fracture criteria have focused on that region. In contrast, failure in low stress triaxialities is relatively unexplored territory in the context of large-scale crash analysis. The probability of this failure mode increases with the decreasing ductility that is characteristic of high and extra high strength steels. Therefore, ductile fracture simulations are performed with large thin-walled steel structures employing four different fracture criteria that differently account low stress triaxialities and deformation history. Criteria are compared as to their capabilities to reproduce and predict experimentally measured behaviour. Analyses demonstrate that failure under lower stress triaxialities affects the response significantly especially when complex deformation history is considered. Suggestions are made for the further enhancement of fracture criteria as well as experimental configurations employed for benchmarking failure criteria.

Cracking load of high strength ECC-steel composite bridge deck with impact of shrinkage stress—Test and simulation

In this paper, developed high strength engineered cementitious composite (HSECC) with low drying and autogenous shrinkage characteristics was used in HSECC-steel composite bridge decks. The flexural performance of the composite element, especially the cracking load of the HSECC layer, is investigated by experiments. In the study, two kinds of cement, normal Portland cement (OPC) and calcium sulfoaluminate cement (SAC) that possesses extra high early-age strength, were used respectively as cementing material in HSECCs. The effect of shrinkage of HSECC on cracking load of the HSECC layer in the structure is evaluated. The test results show that the shrinkage of HSECC in the composite structures will result in obvious shrinkage stresses, which will greatly reduce the cracking load of HSECC layer in the structures. The use of internal curing with pre-wetted calcined zeolite particles will greatly reduce the autogenous and drying shrinkage of HSECC, which in turn, can effectively reduce the shrinkage stress and enlarge the cracking load in the structures. The developed numerical method on shrinkage stress and mechanical loading capacity coupled with shrinkage load can be used in analyses of composite structures. Based on numerical calculation, after coupling with shrinkage stress, the highest and lowest load carrying capacity as cracking of the HSECC-steel composite deck at 28 days may be achieved as 91.91, 47.04 kN and 86.13, 6.17 kN respectively under sealed and drying.

Investigation Effect of Type, Property and Dimension of Stiffener Perforated Steel Shear Wall

Steel plate shear wall (SPSW) according extra ductility and high strength and lateral stiffness and improved behavior in plastic stage recognized as a good lateral system for building structure, particularly as it interests with earthquake resistant design. Improvise of opening is one advantage of this system. The researchers on perforated steel plate shear wall have shown that the shear strength and stiffness of an un-stiffened steel shear wall decrease due to perforation of the infill plate. So stiffener leads to increasing stability of structural system of buckling and strength, lateral stiffness. To this research still plate shear wall with opening that can be of different material such as rebar, steel plate also effect of increase and decrease of steel plate section area and effect of its dimension studied. Analysis result was observed that applying steel plate with similar area, leads to more ultimate strength. In additionally ultimate strength increase when area increased. With comparing of result of stiffeners dimension due maximum ultimate shear strength. Finally suggest optimum aspect ratio (b/t).

Seismic failure probability of a 400kV power transformer using analytical fragility curves

Abstract Recent earthquakes have shown that Electrical Power Substations' equipment are seismically vulnerable, resulting in disruption of power supply in many cases, and therefore their seismic vulnerability evaluation is of great importance. Power transformers (PTR) are critical elements in a power substation, so their proper functioning during and after earthquakes is essential. In this study first, seismic vulnerability of PTRs in past earthquakes is reviewed and failure modes are discussed, then 3D finite element modeling and time-history analysis were performed using 99 three-component original accelerograms of ground motions. Seismic analytical fragility curves of a 400 kV PTR are obtained in two damage states using Multiple Stripes Analysis method which estimates the fragility values while minimizing the required number of structural analysis. The results show that using extra high strength C130 porcelain, the PTR's bushing wouldn't encounter with moderate damage and it might be also acceptable for ground motions with peak ground acceleration (PGA), lower than 0.4 g. It can also be expressed that utilizing specific seismic considerations such as base-isolation, providing dampers or using composite bushing is necessary for PTR's porcelain bushing in seismic regions (PGAs ≥ 0.5 g).

Super and hyper duplex stainless steels: structures, properties and applications

In oil-gas industry, the exploration and development are now targeted to the deep reservoirs with high pressures, high temperatures and extreme corrosive environments. This requires that the materials used should have a good combination of extra high strength and excellent corrosion resistance. In order to meet these challenges, hyper duplex stainless steels have recently been developed. These materials have nitrogen contents up to about 0.5% and PRE-values close to 50, and show both highest corrosion pitting resistance and highest strength among the existing duplex stainless steels.The purpose of this paper is to provide an overview on hyper duplex stainless steels. It will mainly focus on the material development, microstructures, corrosion properties such as critical pitting corrosion temperature and crevice corrosion resistance, heterogeneous deformation behaviour of duplex stainless steel, and mechanical properties such as tensile properties and fatigue properties. These properties and the ratios of strength/weight will then be compared with those of other type of duplex stainless steels. The potential applications for hyper duplex stainless steels are also discussed.

DOMEX 700W

Abstract Domex 700W is an extra high strength member of the Domex family of cold-forming steels, which are thermomechanically rolled and where all the processing is carefully controlled. The Domex alloys are advanced high-strength steels that reduce the weight of heavy vehicles, trailers, cranes, and containers. The "W" signifies a weather-resistant steel. This datasheet provides information on composition, physical properties, tensile properties, and bend strength as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: SA-705. Producer or source: SSAB Swedish Steel Inc..

Microstructure and Mechanical Properties of Extra High Strength Heavy Steel Plate for Bridge Application

Key parameters for thermomechanical control process (TMCP) and integrated welding operations have been determined to industrialize extra high strength micro-alloyed low carbon SiMnCrMoNiCu steel plates for bridge applications. Confocal Scanning Microscope was used to make In-situ observation on austenite grain growth during reheating. A Gleeble 3800 thermomechanical simulator was employed to investigate transformation behavior of the TMCP conditioned austenite. Integrated industrial rolling trial was conducted to correlate the laboratory observations and commercial production of the plates. Microstructure factors affecting the toughness of the steel were analyzed. Submerged-Arc Welding (SMAW) trails were conducted and the structures and mechanical properties of the weld joints characterized. The representative plate with thickness of 60 mm consisted of acicular ferrite (AF) + refined polygonal ferrite (PF) + granular bainite (GB) across the entire thickness section exhibit yield strength (YS) greater than 560 MPa in transverse direction and excellent Charpy V Notch (CVN) impact toughness greater than 100 J at-40 °C in the parent metal and the weld joints. These provide useful integrated database for producing advanced high strength steel plates via TMCP. Keywords: Thermo-Mechanical Control Process;Weathering Steel Plate for Bridge; Submerged-Arc Welding without Preheating

FEA Simulation Analysis of Tube Hydroforming Process Using DEFORM-3D

Tube hydro-forming (THF) one of the attractive forming process for the production of hollow tubes. number of applications of THF are known in the automotive and aerospace industry where more intricate geometries formed from tubes and extrusions. They are characterized by the use of tubes, thus allowing an extended different variety of shapes. Now a day, the automotive industry is showing interest in THF. The benefits of THF can, for instance, be combined with the high strength of extra high strength steels, which are usually less formable, to produce structural automotive components which exhibit lower weight and improved service performance. Design and production of tubular components require knowledge about tube material behaviour and tribological effects during hydro-forming and how the hydro-forming operation itself should be controlled.The THF process is a relatively complex manufacturing process; the performance of this process depends on various factors and requires proper combination of part design, material selection and boundary conditions. Due to the complex nature of the process, the behaviour of the process will be done in the simulation study. The simulation model will be prepared and analyzed by FEM tool DEFORM-3D. The main object of the proposed study is to examine the influence of various factors like friction between the dies and tube blank, axial plunger feeding and internal pressure on bulge height and thickness variations by using DEFORM-3D solver.

DOMEX 550W

Abstract Domex 550W is an extra high strength member of the Domex family of cold-forming steels, which are thermomechanically rolled and where all the processing is carefully controlled. The alloy is used in cold formed and welded products. The Domex alloys are advanced high-strength steels that reduce the weight of heavy vehicles, trailers, cranes, and containers. The "W" signifies a weather resistant steel. This datasheet provides information on composition, physical properties, tensile properties, and bend strength as well as fracture toughness. It also includes information on forming, heat treating, and joining. Filing Code: SA-688. Producer or source: SSAB Swedish Steel Inc..

Conical tube hydro‐forming design of automotive instrument panel beams using computer aided engineering

AbstractThe hydroforming technology has been spreaded dramatically in automotive industry during the last 10 years. The advantages of hydroforming (less thinning, a more efficient manufacturing process, etc.) can, for instance, be combined with the high strength of extra high strength steels, which are usually less formable, to produce structural automotive components, which exhibit lower weight and improved service performance. Design and production of tubular components require knowledge about the tube material and forming behavior during hydroforming and how the hydroforming operation itself should be controlled. These issues are studied analytically in the present paper. In this study, the whole process of automotive IP (instrument panel) beam parts development by conical tube hydroforming using a steel material having a tensile strength of 370 MPa grade is presented. At the part design stage, it requires feasibility study and process design aided by CAE (computer aided engineering) to confirm the hydroformability in details. Effects of parameters such as geometry shape in automotive IP parts on the hydroforming process were carefully investigated. The overall feasibility of hydroformable IP parts could be examined by cross sectional analyses. Moreover, it is essential to ensure the formability of the tube material on every forming step such as pre‐bending, preforming and hydroforming. In addition, all the components of the prototyping tool are designed and the interference with the press is examined from the point of geometry and thinning.

Influence of Thermal History on Microstructure and Mechanical Properties of Steels for Hot Stamping

Hot stamping is an attractive method to produce extra high strength automotive components. In the conventional hot stamping, the furnace heating is employed and the heating rate is quite low. To improve the productivity of the hot stamping technology, the reduction of time for the heating process is required. In this study, the influence of the heating rate in a range up to 200°C/s, heating temperatures between 650°C and 950°C and cooling condition on microstructure and mechanical properties of 0.22% C -3%Mn steel has been investigated. The steel is a promising material for the highly productive new hot stamping technology because this steel transformed into martensite from austenite even at cooling in free air. The specimens heat-treated at a high heating rate and for short holding time at the heating temperature just above Ac3 show significantly fine martensite microstructure and a good strength-toughness balance. In this paper, the α→ γ transformation behavior and the γ→ α transformation behavior after inter-critical annealing are discussed to explain the evolution of the microstructures and mechanical properties.

Effect of aging temperature on modulated structures of 00Ni 12Cr 5Mo 3TiAlV maraging steel

Effect of aging temperature on modulated structures of Co-free 00Ni 12Cr 5Mo 3TiAlV maraging steel was studied. With increasing the aging temperature, the modulated structures become more obvious. When the temperature is lower, the occurrence of spinodal decomposition only can be indicated by a little elongation of diffraction spots. However, when the temperature is higher, the in situ intermetallic precipitates of modulated structures are distributed along 0 1 0 direction (the elastic soft direction). The coherent relationship was kept between matrix and precipitates. The extra high strength and good ductility are mainly attributed to the in situ precipitation strengthening and coherent effect of modulated structures.