HY-100 Steel Research Articles

Temperature-Dependent Material Property Databases for Marine Steels—Part 3: HSLA-80

Integrated Computational Materials Engineering (ICME)-based tools and techniques have been identified as the best path forward for distortion mitigation in thin-plate steel construction at shipyards. ICME tools require temperature-dependent material properties—including specific heat, thermal conductivity, coefficient of thermal expansion, elastic modulus, yield strength, flow stress, and microstructural evolution—to achieve accurate computational results for distortion and residual stress. However, the required temperature-dependent material property databases of US Navy-relevant steels are not available in the literature. Therefore, a comprehensive testing plan for some of the most common marine steels used in the construction of US Naval vessels was completed. This testing plan included DH36, HSLA-65, HSLA-80, HSLA-100, HY-80, and HY-100 steel with a nominal thickness of 4.76 mm (3/16-in.). This report is the second part of a seven-part series detailing the pedigreed steel data. The first six reports will report the material properties for each of the individual steel grades, whereas the final report will compare and contrast the measured steel properties across all six steels. This report will focus specifically on the data associated with HSLA-80 steel.

Shear band formation in porous thin-walled tubes subjected to dynamic torsion

In this paper, we have performed 3D finite element calculations of thin-walled tubes subjected to dynamic twisting to investigate the effect of porous microstructure on the formation of shear localization bands under simple shear conditions. For that purpose, we have incorporated into the finite element model the porous microstructures of four different additive manufactured metals – aluminium alloy AlSi10Mg, stainless steel 316L, titanium alloy Ti6Al4V and Inconel 718 – for which the void volume fraction varies from ≈0.001% to ≈2%, and the voids size between ≈6μm and ≈110μm (Marvi-Mashhadi et al., 2021). For each microstructure, we have created up to 10 realizations varying the spatial location of the voids and the distribution of voids size. The matrix material is elastic/plastic, with yielding defined by the von Mises yield criterion and associated flow rule. The yield stress evolution is considered to be dependent on strain, strain rate and temperature, with parameters corresponding to Titanium and HY-100 Steel, taken from Molinari (1997) and Batra and Kim (1990), respectively. Moreover, we have assumed the deformation process to be adiabatic. The calculations have been performed for shear strain rates ranging from 100s−1 to 10000s−1. To the authors’ knowledge, this is the first study ever that simulates dynamic torsion testing of porous materials with actual representation of voids, providing new results which bring to light the influence of porosity on dynamic shear banding under simple shearing. Namely, the numerical calculations have shown that both the location of the shear band and the critical strain leading to the shear band formation depend on the spatial and size distribution of the voids in the specimen, evidencing the influence of material defects on the localization pattern. Notably, the shear band nucleation strain decreases with both the void volume fraction in the specimen and the size of the voids, the size of the largest pore being the main microstructural feature controlling the loss of load carrying capacity of the specimen. In addition, we have carried out a parametric analysis varying the temperature and strain rate sensitivities of the material, and the loading rate. For the strain rates investigated, increasing the loading speed leads to a mild decrease of the shear strain leading to shear band formation, while the strain rate sensitivity is shown to stabilize material behavior and delay localization. Moreover, the numerical results have made apparent that for the hardening materials considered, thermal softening is essential to trigger the shear band formation, so that the porous microstructure alone does not lead to shear localization.

Effects of geometry and material factors on the behavior of stiffened offshore pipe structures under hydrostatic pressure

The world's oil and gas sectors are diverse. They utilize offshore pipes to generate millions of barrels of oil and gas to meet global energy demands. In this study we identified the critical buckling load that occurred on a cylinder shell (also known as radial buckling). Offshore pipe design must meet several criteria, one of which is the requirement for pipes to withstand the external hydrostatic pressure of seawater. The overall buckling load is calculated using the axial compression loading and the pressure on the entire surface of the cylinder shell (radial compression). The finite element analysis (FEA) method is used in our simulation. FEA is run using ABAQUS/CAE software with the Riks algorithm. Different types of cylinder shells are used in the simulation: unstiffened, stringer-stiffened, and ringstiffened. The cylinder shell is loaded based on the depth of the installation. The material composition of the shell is varied with API 5L X65, copper-nickel alloy, and HY100 steel. The diameter sizes used are 28" (711.2 mm), 30" (762 mm), and 32" (812.8 mm). The simulation results show a critical buckling load for each variation. The critical buckling load is determined by the Young's modulus, geometric length, and moment of inertia. Based on the critical buckling loads generated, we also identify which cylinder shell composition is the strongest.

Application of Macro-Instrumented Indentation Test for Superficial Residual Stress and Mechanical Properties Measurement for HY Steel Welded T-Joints.

HY-80 and HY-100 steels, widely used in constructing large ocean vessels and submarine hulls, contain mixed microstructures of tempered bainite and martensite and provide high tensile strength and toughness. Weld integrity in HY steels has been studied to verify and optimize welding conditions. In this study, the T-joint weld coupons, HY80 and HY100, were fabricated from HY-80 and HY-100 steel plates with a thickness of 30 mm as base metals by submerged-arc welding. Flux-cored arc welding was performed on an additional welding coupon consisting of HY-100 to evaluate the effect of repair welds (HY100RP). Microstructures in the heat-affected zones (HAZ) were thoroughly analyzed by optical observation. Instrumented indentation testing, taking advantage of local characterization, was applied to assess the yield strength and the residual stress of the HAZ and base regions. The maximum hardness over 400 HV was found in the HAZ due to the high volume fraction of untempered martensite microstructure. The yield strength of the weld coupons was evaluated by indentation testing, and the results showed good agreement with the uniaxial tensile test (within 10% range). The three coupons showed similar indentation residual stress profiles on the top and bottom surfaces. The stress distribution of the HY100 coupon was comparable to the results from X-ray diffraction. HY100RP demonstrated increased tensile residual stress compared to the as-welded coupon due to the effect of the repair weld (323 and 103 MPa on the top and bottom surfaces). This study verifies the wide applicability of indentation testing in evaluating yield strength and residual stress.

Temperature-Dependent Material Property Databases for Marine Steels—Part 1: DH36

Integrated computational materials engineering (ICME)-based tools and techniques have been identified as the best path forward for distortion mitigation in thin-plate steel construction at shipyards. ICME tools require temperature-dependent material properties to achieve accurate computational results for distortion and residual stress. However, the required temperature-dependent material property databases of U.S. Navy-relevant steels are not available in the literature. Therefore, as part of a Lightweight Innovations for Tomorrow program, a comprehensive testing plan for some of the most common marine steels used in the construction of US naval vessels was completed. This testing plan included DH36, HSLA-65, HSLA-80, HSLA-100, HY-80, and HY-100 steel with a nominal thickness of 4.76 mm (3/16-in.). This report is part of a seven-part series detailing the pedigreed steel data. The first six reports will report the material properties for each of the individual steel grades, whereas the final report will compare and contrast the measured steel properties across all six steels. This report will focus specifically on the data associated with DH36 steel.

The collective behavior of shear strain localizations in dipolar materials

We study the collective behavior of shear bands in HY-100 steel and OFHC copper taking into account the dipolar effects. Starting from mathematical model, we present new numerical methodology that allows one to simulate the processes of shear strain localization in nonpolar and dipolar materials. The verification procedure was performed to prove the efficiency and accuracy of the proposed method. Using the proposed algorithm we investigate the statistical characteristics of the shear strain localization processes in dipolar materials and compare results with nonpolar case. In particular, we obtain the statistical distributions of the width of localization zones and distance between them.

Selective laser melting of HY100 steel: Process parameters, microstructure and mechanical properties

Selective Laser Melting (SLM) of a high strength low alloy steel HY100 is considered in the present investigation. The current work describes (i) optimization of SLM process parameters for producing fully dense parts in HY100 steel and (ii) the effects of post-processing heat treatment on the microstructure and mechanical properties. Samples have been fabricated by SLM using different combinations of laser power, laser scan speed, and hatch spacing. Fully dense samples were achieved at an energy density of 65J/mm3. Microstructures of the as-built and heat treated samples were investigated using optical and scanning electron microscopes, X-ray diffraction, and electron backscattered diffraction techniques. The as-built sample showed fully martensitic microstructure with alternate bands of untempered (hard) and auto-tempered (soft) regions. The as-built parts are unsuitable for direct application due to untempered, hard and brittle martensite microstructure. The as-built parts were subjected to post-processing heat treatments (“direct temper” and “quench and temper”). The direct tempered samples exhibited higher yield strength and ultimate strength than the quench and temper ones. Noticeable amounts of anisotropy with respect to the build orientation, especially in tensile elongation, were observed in the direct tempered samples due to in-homogenous microstructure. Quench and temper treatment of the parts resulted in recrystallized grains with uniform microstructure. The current investigation shows that quench and temper at 650°C is an optimum post processing treatment for HY100 SLM parts as it manifests desired strength with good tensile elongation.

Finite Element Cold Bending Residual Stress Evaluation on Submarine Pressure Hull Instability Assessment

During the pressure hull manufacturing, processes like cold bending and welding are often applied. These processes lead to permanent plastic deformations which are associated with residual stresses. The presence of residual stresses is equivalent to the introduction of an initial preload in the structure, which accelerates the plastification process, decreasing pressure hull resistance. To quantify this reduction, a case study that considers residual stresses due to cold bending on hull plates and frame flanges had been performed using finite element models. The study encompasses hull diameters of 6, 8, and 10 m with hull plates and frame flange thickness from 20 to 30 mm, with HY100 steel. Finite element numerical analyses were done considering material and geometric nonlinearities. First, the cold bending residual stresses were determined using finite element models. Then, these cold bending residual stresses were introduced as initial stresses in the submarine pressure hulls' finite element models. In the end, it was possible to verify that the presence of cold bending residual stress reduces the submarine hull collapse pressure up to 4.3%.

Self-organization of adiabatic shear bands in OFHC copper and HY-100 steel

We study the self-organization process of adiabatic shear bands in OFHC copper and HY-100 steel taking into account strain hardening factor. Starting from mathematical model we present a new numerical approach, which is based on Courant–Isaacson–Rees scheme, that allows one to simulate fully localized plastic flow. To prove the accuracy and efficiency of the following method we give solutions of two benchmark problems. Next we apply the proposed method to investigate such quantitative characteristics of self-organization process of ASB as average stress, temperature, localization time and distance between ASB. Then we compare the obtained results with theoretical predictions by other authors.

Influence of Dissipated Energy on Shear Band Spacing in HY-100 Steel

To analyze the formation of multiple shear bands in HY-100 steel, we consider an infinitely extended layer of finite thickness subjected to shear loading. The perturbation approach, associated with numerical methods, is used to determine the instability modes. The criteria of Wright–Ockendon and Molinari are used to determine the shear band spacing. The hypothesis consisting in considering the proportion of plastic work dissipated as heat (quantified by the Taylor–Quinney coefficient β) as independent of the loading path is now recognized as highly simplistic. The present study attempts to provide a systematic approach to the inelastic heat fraction evolution for a general loading within the framework of thermoviscoplastic standard modeling, including a number of material parameters as strain hardening, strain rate sensitivity, and thermal softening. The effect of each material parameter on the shear band spacing is determined by using a power law constitutive relation. The Johnson–Cook and power law models are used to illustrate the influence of the constitutive relation on the results for the adiabatic shear band spacing by studying the response of HY-100 steel. We have compared our results with available experimental results in the literature over a very wide range of strain rates (103–105 s−1). In this study, we show that the variation in the Taylor–Quinney parameter β(γ) as a function of shear strain is an important parameter that plays a significant role in the calculation of the shear band spacing.

잠수함 압력선체의 피로강도에 대한 실험적 연구

Submarine and deep sea diving structures are generally designed based on their ultimate strength. Fatigue strength at welded joint must be also taken into account because working stress is increased due to the increasing of diving depth and using high yield steel. The pressure hulls of submarine are subjected to fluctuating compressive loading. But in addition to the calculated stresses, high residual tensile stresses at welded part have to be considered. The state of stress level of pressure hull is tensile at surface and compressive at deep diving depth. This paper presents the results of an experimental investigation on the crack initiation and growth at the weld toe of T welded joints of HY-100 steel plate under constant amplitude loading. It is also investigated the phenomenon of the fatigue failure and test methods. Fatigue tests have been using real scaled local structural models of full penetration T-welded joint, which is a part of the cylindrical shell structures reinforced by ring stiffeners. Several load ratios under constant amplitude loading are considered in the tests. Crack initiation and growth characteristics are examined based on the beach marks of the cracked section of the test specimens. A design stress-life curve including the design formula is suggested according to tested data.

Influence of anisotropy (crystallographic and microstructural) on spallation in Zr, Ta, HY-100 steel, and 1080 eutectoid steel

The purpose of this study is to quantify the influence of textural and microstructural anisotropy on spallation. This includes the influence of anisotropically-oriented MnS inclusion stringers in the HY-100 and 1080 steels on spallation, within two crystallographically-isotropic steels, and the influence of strong, anisotropic crystallographic texture in high-purity polycrystalline Ta and Zr materials to assess the role of texture on damage evolution and spallation responses. The effect of anisotropic crystallographic texture on the spallation response of Ta and Zr is shown to play a minimal role in the spallation response of each material, as seen in wave profile pull-back signals, compared to the effect of texture on the shock arrival time and the Hugoniot elastic limit that reflects strength in these two high-purity materials. In the case of both the 1080 and HY-100 steels, the influence of elongated MnS stringers, resident within the essentially crystallographically isotropic steels, was found to be dominated by the heterogeneous nucleation of damage orthogonal to the MnS stringers. Delamination between the pearlitic matrix microstructure and the MnS stringers in the 1080 steel, or inclusions and the martensitic matrix in the HY-100 steel, was seen to correlate to a lower pull-back signal during transverse loading than to that parallel to the stringer axis in each steel.

Crack arrest testing of high strength structural steels for naval applications

The crack arrest fracture toughness of two high strength steel alloys used in naval construction, HSLA-100, Composition 3 and HY-100, was characterized in this investigation. A greatly scaled-down version of the wide-plate crack arrest test was developed to characterize the crack arrest performance of these tough steel alloys in the upper region of the ductile–brittle transition. The specimen is a single edge-notched, 152 mm wide by 19 mm thick by 910 mm long plate subjected to a strong thermal gradient and a tensile loading. The thermal gradient is required to arrest the crack at temperatures high in the transition region, close to the expected service temperature for crack arrest applications in surface ships. Strain gages were placed along the crack path to obtain crack position and crack velocity data, and this data, along with the applied loading is combined in a “generation mode” analysis using finite element analysis to obtain a dynamic analysis of the crack arrest event. Detailed finite element analyses were conducted to understand the effect of various modeling assumptions on the results and to validate the methodology compared with more conventional crack arrest tests. Brittle cracks initiation, significant cleavage crack propagation and subsequent crack arrest was achieved in all 15 of the tests conducted in this investigation. A crack arrest master curve approach was used to characterize and compare the crack arrest fracture toughness. The HSLA-100, Comp. 3 steel alloy had superior performance to the HY-100 steel alloy. The crack arrest reference temperature was T KIA = −136 °C for the HSLA-100 plate and T KIA = −64 °C for the HY-100 plate.

A critical shear displacement criterion for ductile–brittle transition under mixed mode I and II loading

Micromechanisms producing ductile and brittle damage operate in parallel at a crack tip. The dominant mode of failure depends upon which of the two (ductile or brittle) damage parameters first reaches its critical value. This has been shown by a study of ductile–brittle transition behaviour in HY100 steel under mixed mode I and II loading. The transition from ductile to brittle behaviour in HY100 steel was found to be affected by mixed mode I and II ratio (ratio of imposed tensile and shear loading) in a manner such that with increasing shear the transition temperature decreased. In the present paper, a criterion is proposed based on the shear strain ahead of a notch tip, to predict the fracture behaviour at any given temperature and mixed mode ratio.

A physically based model for dynamic failure in ductile metals

It is well established that high rate failure of structural materials takes place by rate processes occurring at the microscopic level and involving nucleation, growth, and coalescence of voids or cracks. At the submicroscopic level, the mechanism of failure in polycrystalline metals is often dislocation controlled. In the present work, we propose a physically based model describing these processes at high deformation rate such as under the planar impact test. This model combines the mechanical threshold stress (MTS) theory for the evolution of the flow stress and a mechanistic model for failure behavior by cumulative nucleation and growth of voids. This paper describes the approach used to obtain the constitutive equations and the resulting computational modeling for predicting dynamic failure in ductile metals. The model formulation is three-dimensional and is suitable for a general state of stress and strain. Results from the simulations of the planar impact problems for different configurations are presented and compared with the experimental results for OFHC copper and HY-100 steel. This comparison shows the model capabilities in predicting the experimentally measured free surface velocity profile as well as the observed spall pattern respectively in the copper target of a planar impact test and in the steel target of a plate-conic impact. We have also compared the results from this model to those of the phenomenological model of Johnson–Cook.

The Influence of Material Models on Finite Element Simulation of Machining

In literature, four models incorporating strain rate and temperature effects are able to generalize material test results of HY-100 steel. This study compares the four models, namely, Litonski-Batra, power law, Johnson-Cook, and Bodner-Partom, in finite element modeling of orthogonal machining of this material. Consistency is found in cutting forces, as well as in stress and temperature patterns in all but the Litonski-Batra model. However, the predicted chip curls are inconsistent among the four models. Furthermore, the predicted residual stresses are substantially sensitive to the selection of material models. The magnitudes, and even the sign of the residual stresses in machined surfaces, vary with different models.

Influence of the material constitutive models on the adiabatic shear band spacing: MTS, power law and Johnson–Cook models

We propose to use the physically-based mechanical threshold stress (MTS) model for the analysis of adiabatic shear band spacing in HY-100 steel and Ti–6Al–4V alloy. Based on existing works, we use the perturbation method to determine the instability modes and their corresponding spacing. To validate our results, we compare them to those obtained using the phenomenological, and widely used, Johnson–Cook and power law models. We notice that the shear band spacing depends on the constitutive relation employed. We also compared the results from our analytical analysis to the available experimental ones. We show, for the first time, that the MTS model yields good results for adiabatic shear band spacing, particularly for the case of Ti–6Al–4V alloy.

Damage accumulation and failure of HSLA-100 steel

Damage accumulation in the form of the volume fractions and number densities of strain-induced voids has been experimentally characterized for HSLA-100 steel subjected to tensile failure over a range of stress-states (stress triaxiality ratios of 0.8 to 1.4). The dependence of void volume fraction on strain indicates the presence of a void growth stage that is sensitive to stress-state in a manner that can be described by a relationship with the form that can be predicted by Rice and Tracey but with an increased dependence on stress triaxiality. The damage results also suggest a transition of stable void growth to rapid void growth and imminent material fracture at a critical void volume fraction that decreases slowly with increasing stress triaxiality ratio. A straight-forward analysis, based on the experimental observations, relates the observed experimental dependence of failure strains on stress triaxiality for this steel. The damage accumulation behavior of this steel, which fails due to the growth and coalescence of equiaxed voids, is also contrasted to that of HY-100 steel which forms elongated voids.

Modeling void coalescence during ductile fracture of a steel

Ductile fracture of HY-100 steel at high stress triaxialities occurs by a void-sheet mode of failure in which large elongated voids, formed at MnS inclusions, coalesce as a result of a localized deformation instability that develops between neighboring voids. In this study, micro-mechanical modeling using finite element analysis has been employed to examine the deformation localization behavior within void arrays based on experimentally observed inclusion microstructures of HY-100 steel. Treating the elongated voids as through-thickness holes, we utilize image-based multi-hole models, each depicting roughly 125 voids, to identify the significance of the critical features (size, spacing, clustering) of the void microstructure on the deformation localization process and ultimately void-sheet coalescence and failure. The deformation localization is especially sensitive to the presence of a few large voids spaced within roughly 30 hole diameters of each other and oriented on planes 45°±15° to the maximum applied principal stress. The results also show that deformation localization develops more readily at high stress triaxialities. Smaller, “secondary” voids can promote the onset of strain localization between large voids, even if they nucleate after a rather large void nucleation strain. Within microstructures consisting of solely of small voids, high density clusters can cause intense strain localization, but it is confined within the scale of the cluster.

Cellular automata simulation of microstructural evolution during dynamic recrystallization of an HY-100 steel

Microstructural evolution and plastic flow characteristics of an HY-100 steel were investigated using a simulative model that couples the basic metallurgical principle of dynamic recrystallization (DRX) with the cellular automatIon (CA) method. Variation of dislocation density with local strain of deformation is considered for accurate determination of the microstructural evolution during DRX. Macro-stress–strain relationship was calculated from the average of local stresses and strains. The predictions show very good agreement with the experimental results for the steel.