High Strength Stainless Steel Research Articles

Patch-loading resistance of QN1803 and S32001 high-strength stainless steel plate girders: Experimental study and numerical simulation

Patch-loading resistance of QN1803 and S32001 high-strength stainless steel plate girders: Experimental study and numerical simulation

The effect of strain lag for the flexural enhancement of RC beams strengthened by HMRE under secondary load

This paper presents experimental, numerical and theoretical studies on damaged reinforced concrete (RC) beams strengthened with high-strength stainless steel wire rope (HSSSWR) meshes reinforced engineered cementitious composite (ECC), in order to evaluate the influence of strain lag caused by secondary load on the strengthening effect. Four-point bending tests were first performed to investigate the failure mechanism of HSSSWR meshes reinforced ECC (HMRE) strengthened RC beams under secondary load. Then the parameters were comprehensively studied by finite element (FE) simulation. The results show that even under secondary load, the HMRE can still exhibit good crack-control capacity on concrete and gave significant enhancement in the flexural performance of RC beams. The strain lag of the strengthening layer, which resulted in inadequate utilization of its strength, was intensified with an increase in the initial load level or reinforcement ratio of the longitudinal steel bars, but was mitigated as concrete strength, ECC thickness, reinforcement ratio of HSSSWRs, or HSSSWR ultimate strength increased. Finally, a calculating model was proposed for predicting the bearing capacity of the damaged RC beams strengthened with HMRE, considering strain lag caused by secondary load.

Seismic response of RC short columns strengthened by high-strength stainless steel wire rope meshes reinforced ECC jacket

A novel strengthening scheme of high-strength stainless steel wire rope (HSSSWR) meshes reinforced engineering cementitious composite (ECC) jacket was used to strengthen the reinforced concrete (RC) short columns in this paper. The seismic performance of short columns after being strengthened was investigated, considering the changes in the strengthening scheme, and the spacing of lateral HSSSWRs. The failure mode, hysteresis behavior, envelope curve, ductility, energy dissipation, stiffness degradation, and strength degradation were introduced specifically based on the analysis of six full-scale short columns. The test results show a significant enhancement in the seismic performance of the strengthened short columns, especially in ductility and energy dissipation, which were increased by 49.4–98.4 %, and 149.3–713.2 %, respectively. The placement of HSSSWRs in ECC jacket proved to be effective in enhancing the strengthening effect of the jacket. A prediction model for the shear capacity of the strengthened columns was proposed using the Modified Compression Field Theory (MCFT), and the predicted results were in good agreement with the test results presented in this paper and in relative study.

Comparative performance analysis of straight and harped prestressing seven-wire strands: High-strength stainless steel vs. conventional carbon steel

This paper presents an experimental investigation into the utilization of high-strength stainless steel (HSSS) strands systems in prestressed bridges. The study delves into the effects of localized bent and harping of seven-wire HSSS strand systems under various harping angles and curvatures produced by the deviators. For comparison purpose, conventional carbon steel (CS) strands were also studied using the same experimental parameters. It was anticipated that CS strands would exhibit better performance due to its superior post-yied ductility. To closely mimic the state of practice in the precast plant, two types of deviators were designed and used in this investigation. A comparable harping capacity was observed for HSSS strands relative to CS strands, despite the CS strands exhibiting higher strain compared to the HSSS strands. Upon reaching their breaking load, necking of all seven wires was predominantly observed for HSSS, whereas the CS strands failed due to the fracture of only one or two outer wires. Due to the lack of ductility in the HSSS stand, it was expected to have the lower bent capacity, especially at higher harping angles. Despite the significant difference in post-yied ductility, the study revealed that both HSSS and CS strands exhibit similar performance. To further understand the similarity and difference in behaviour of these two materials, scanning electron microscopy (SEM) examinations were conducted on both HSSS and CS wires to visualize the bending effects on the microstructure level after bending the center wire at different angles.

Optimization the cracking and corrosion resistance of MoSi2 coating by addition of TiVAlZrNb high-entropy alloy on laser powder bed fusion high-strength stainless steel

The MoSi2 coating is an ideal coating system for stainless steel due to its good wear resistance and oxidation resistance in the sea service environment. However, there are always some cracks in the MoSi2 coating due to different thermal expansion coefficients compared with stainless steel, which has an important effect on the corrosion behaviors. In this paper, MoSi2 coatings on laser powder bed fusion (LPBF) high-strength stainless steel prepared by laser cladding technology were optimized by the addition of a TiVAlZrNb high-entropy alloy. The results showed that the addition of a TiVAlZrNb high-entropy alloy could optimize the cracks in the MoSi2 coating by refining the grain size and optimizing the expansion coefficient. The open circuit potential and corrosion potential of the MoSi2 coating were − 158 mV and − 262 mV, respectively, which were lower than those of the composite coating (148 mV and − 225 mV, respectively). The electrochemical impedance value of the MoSi2 coating was higher than that of the MoSi2 + TiVAlZrNb composite coating. The obvious local corrosion originated from the cracks in the MoSi2 coating. Therefore, the addition of TiVAlZrNb high-entropy alloy could optimize the cracking and corrosion resistance of MoSi2 coating on LPBF high-strength stainless steel.

Evaluating the tensile properties of high-strength stainless steels using small punch testing.

Accurately measuring the mechanical properties of high-strength stainless steels is of great significance for ensuring structural safety, predicting long-term performance and optimizing design. However, the standardized tensile test specimens used to obtain strength properties must be fabricated from bulk materials from an in-service structure or component, result in the loss of structural integrity or a reduction in remaining service life. Small punch tests require only miniscule material samples and are widely used to estimate in-service component material characteristics. This study performed small punch tests on three high-strength stainless steels-X17CrNi15-2, 15-5PH, and PH13-8Mo-to obtain the correlations between the small punch tests and the uniaxial tensile test results for each material. The estimated yield stresses obtained from the small punch tests were distributed within a factor of 1.5 on both sides of the unity line when compared with those obtained from the uniaxial tensile tests; the ultimate strength values estimated from the small punch tests correlated quite well with those obtained from the uniaxial tensile tests. An iterative finite element analysis was subsequently established to simulate the small punch tests and thereby obtain the coefficients for a Ludwik power law correlation representing the true stress-strain properties. The finite element predicted force-deflection curves agreed well with the small punch test results, which were also compared with the predictions obtained from empirical equations proposed in previous studies. Finally, the fracture mechanisms of the small punch test specimens were characterized through scanning electron microscopy, indicating that the dimple fracture mechanism dominated the failure mode. The results of this study are expected to inform the application of small punch test to evaluate in-service high-strength stainless steel materials.

Shear resistance of perforated QN1803 high-strength stainless steel plate girders through experimental testing and numerical analysis

QN1803, a high-strength stainless steel, has been developed by steel industry recently. Its tensile yield strength can be approximately 40 % (or more) higher than that of the commonly-used EN1.4301, while its cost is 20 % lower due to its reduced nickel content. One obvious application for QN1803 is in plate girders, where web perforations are often required to accommodate building services. However, no research work has been reported in the literature that investigates the reduced shear buckling capacity of QN1803 plate girders as a result of web perforations. This issue is addressed herein. An experimental program comprising six plate girder tests is conducted in this study. Three different hole ratios were considered: 0.2, 0.4 and 0.6. The depths of web were selected as 700 mm and 500 mm, while the thickness of web was fixed as 4.0 mm. The initial geometric imperfections were determined from three-dimensional (3D) scanning prior to the plate girder tests. Finite element (FE) models incorporating the material non-linearity and initial geometric imperfections were then developed and validated against the experimental results. A parametric analysis including 62 FE models was performed to examine the influences of the critical parameters on the shear buckling capacity of such perforated members. The results suggest that for those members with a hole diameter - web height ratio of 0.6, the shear buckling capacity was reduced by 56 % on average due to the web perforation. The design rules for determining the shear buckling capacity of stainless steel plate girders as specified in Eurocodes (EN 1993–1–4 + A1) (2015) and American Specification (ANSI/AISC 370–21) (2021) were evaluated. Upon comparison, it was demonstrated that both EN 1993–1–4 + A1 (2015) and ANSI/AISC 370–21 (2021) cannot provide accurate and safe predictions for determining the shear buckling capacity of such members.

Material properties and shear behaviour of QN1803 high-strength stainless steel plate girders

QN1803, a high-strength stainless steel, has been developed recently, and its tensile yield strength can be approximately 40 % (or more) higher than the commonly-used EN1.4301, while its cost is 20 % lower due to its reduced nickel content. This high-performance material can potentially be used in many applications, and one such application is plate girders. However, no experimental work has been undertaken. This issue is addressed herein. A detailed experimental study comprising seven plate girder tests is presented in this study. The plates were austenitic grade QN1803 and EN 1.4301, and the depth of web was fixed as 500 mm, 600 mm and 700 mm. For comparison, specimens with rigid end posts were also tested. The initial geometrical imperfections were first determined from three-dimensional (3D) scanning. Finite element models (FEMs) incorporating the material non-linearity and initial geometric imperfections are then developed and validated against the test results. A total of 15 tensile coupon tests are performed to investigate the effects of rolling directions on the material properties, with longitudinal coupons, diagonal coupons, and transverse coupons all being tested. The test results indicated that the 0.2 % proof stresses of the transverse coupons were approximately 8.5 % higher than that of the longitudinal coupons. The plate girder tests suggested that the shear buckling strength of QN1803 members was increased by 38.2 % on average compared to EN 1.4301 members. The design rules for determining the shear buckling strength of plate girders as provided in Eurocodes (EN 1993–1–4 +A1) (2015), North American Specification (ANSI/AISC 370–21) (2021) and those proposed by Chen et al. (2023) were evaluated. The results demonstrated that the design formulas proposed by Chen et al. (2023) can closely calculate the shear buckling strength of such QN1803 members.

Cross-sectional behaviour of QN1803 high-strength stainless steel I-section stub columns in fire

QN1803 is a novel high-strength stainless steel with low nickel. Compared to traditional stainless steel, QN1803 high-strength stainless steel has higher yield strength and lower cost without compromising anti-corrosion properties, thus leading to a wide application prospect. This paper focuses on the cross-sectional behaviour of QN1803 high-strength stainless steel I-section stub columns in fire. A total of eight stub column tests were finished, of which six were elevated temperature tests and two were room temperature control tests. Room temperature and elevated temperature tensile coupon tests were conducted to obtain the material properties of the QN1803 high-strength stainless steel. The design methods of European fire design standard EN 1993-1-2 and the latest fire design methods proposed by Xing et al., which will be incorporated into the upcoming version of EN 1993-1-2, were evaluated in terms of accuracy and safety for the fire design of QN1803 high-strength stainless steel I-section stub columns. It was found that most ultimate cross-sectional resistances of QN1803 high-strength stainless steel I-section stub columns predicted by the design rules of European fire design standard EN 1993-1-2 were unsafe, while the ultimate cross-sectional resistances predicted by the design methods of Xing et al. were safe and accurate for the tested QN1803 high-strength stainless steel I-section stub columns.

Numerical investigation and design method of cold-formed sorbite stainless steel circular tubes under uniaxial compression

The recently developed novel high-strength sorbite stainless steel (S600E) combines the advantages of exceptional mechanical properties, high corrosion resistance, effortless weldability, and cost-effectiveness, granting remarkable competitiveness in stainless steel structures. The authors have conducted and published experiment results on S600E circular hollow section (CHS) columns under uniaxial compression, which serve as a foundation for the subsequent numerical analysis presented in this study. An extensive parametric study encompassed key variable parameters such as slenderness ratio, section size, and diameter-to-thickness ratio, culminating in 748 numerical models. Meanwhile, the ultimate strength obtained through finite element analysis (FEA) was utilized to evaluate the calculation methods prescribed by current European, Australian/New Zealand, and Chinese stainless steel structural design standards and the direct strength method (DSM) available in the literature. The result shows that the DSM can accurately predict the ultimate strength of CHS columns with an average error of 0.2%, while other specifications are slightly conservative. Then, the effective area calculation method was proposed in this paper, whose rationality was verified by meso finite element analysis. Moreover, a revised equation in Chinese code was proposed, which can improve the prediction accuracy by 9.2%. Finally, a reliability analysis was conducted to assess the safety levels of the design standards and DSM. The findings of this study can not only benefit the adoption of the high-strength stainless steel in the construction industry and therefore potentially mitigate carbon-emission-related environmental issues.

Nonlinear Inelastic Stability Behavior of High-Strength Stainless Steel I-Beams with Sinusoidal Web Openings

Perforated beams can bring countless benefits compared to traditional plain-webbed beams. However, steel beams with sequential web openings are more susceptible to instabilities, and special care must be taken in a design concerning the failure modes these structures can present. The study presented herein explicitly dealt with the stability behavior of perforated beams with sinusoidal openings. This type of perforated member features smooth-lined openings constructed from a single thermal cut in conventional plain-webbed steel profiles. A broad study was carried out through numerical simulation using the ABAQUS software, in which perforated profiles manufactured with S600E high-strength stainless steel were studied. The use of high-strength steels in perforated profiles is a little explored topic in the literature, despite having a significant impact on the behavior of these elements. With the study carried out, a broad overview of the stability behavior of these members was obtained, especially concerning global stability. A total of 5940 FE models were developed, considering the application of different types of loads. In these models, linear buckling analysis (LBA) and geometrically and materially nonlinear analysis with imperfections (GMNIA) were performed. The results obtained were compared with international design codes, and it was found that some codes fail to represent the behavior of members that present lateral-distortional buckling (LDB) and interactions between local and global failure modes. This behavior is a significant design concern since the studied members had high yield strength, making them more susceptible to interaction-governed failure modes than usual-yield strength members. Additionally, the study found that some design codes do not accurately represent the behavior of members loaded outside the shear center due to the destabilizing effect of loading on these structures.

The effect of multiscale second-phase particles on the corrosion behavior of laser powder bed fusion high strength stainless steel

The second-phases have a significant impact on the pitting behaviors of laser powder bed fusion (LPBF) high strength stainless steel. The size, composition and interface characteristics of multiscale second-phases and effects on the pitting mechanisms were studied in this paper. The results showed that there were Si-rich irregular inclusions, spherical oxides inclusions, NbS/NbS-Mn particles and 3–5 nm (Cu, Nb)-rich precipitates for LPBF high strength stainless steel. The surface potential of the irregular inclusions was 67 mV higher than that of martensite and the obvious microcracks or gaps at the interface between irregular inclusions and matrix were observed. The pitting resistance and electrochemical impedance value of LPBF high strength stainless steel was lower than that of conventional samples due to galvanic corrosion and the gap defect for high content of irregular inclusions.

Onto the role of copper precipitates and reverted austenite on hydrogen embrittlement in 17-4 PH stainless steel

High strength materials are of interest for hydrogen powered mobility where structural components can be exposed to high pressure (350–700 bars) of dihydrogen. However, high strength stainless steels such as 17-4 PH grade with a martensitic matrix are known to be more prone to hydrogen embrittlement (HE). The mechanisms affecting this type of grade have not been completely elucidated yet. In particular, in this work, the role of copper rich precipitates (Cu-pp) and reverted austenite (γrev) on mechanical behavior in presence of hydrogen was investigated. At first, advanced structural characterizations (Synchrotron-XRD, ACOM/TEM) were performed on different metallurgical conditions. Then, hydrogen trapping ability of Cu-pp and γrev was investigated using thermal desorption spectroscopy (TDS). Hydrogen embrittlement susceptibility was qualified through slow strain rate tensile testing. The results showed that the formation of tiny Cu-pp (< 10 nm) during ageing was deleterious for the HE resistance of the steel, since it increased the ultimate tensile strength. In addition to their role in the steel hardening, tiny Cu-pp actively trapped hydrogen at the Cu-pp/matrix interfaces. The nature of Cu-pp/matrix interfaces, which affects their surface energy and therefore the binding energy of hydrogen, impacted clearly the HE resistance. In particular, TDS experiments showed that tiny ‘slightly coherent’ Cu-pp acted as a low energy hydrogen trap contrary to tiny ‘incoherent’ fcc Cu-pp which strongly trapped hydrogen. The former was found to have a deleterious effect while the latter had a rather beneficial effect. Besides, a high fraction of reverted austenite was beneficial for the HE resistance since it softened the material, and trapped rather strongly hydrogen at the γrev/matrix. The fcc (Cu-pp or γrev)/martensitic matrix interfaces seemed to play a major role in hydrogen trapping in 17-4-PH stainless steel. When hydrogen is tightly bound to these interfaces, it happens to reduce the hydrogen embrittlement susceptibility of the material, 17-4 PH that is generally ‘H fragile’ because of its martensitic matrix.

Seismic performance of RC columns strengthened with HSSSWR meshes reinforced ECC under high axial compression ratio

The cyclic loading tests under high axial compression ratio were performed to investigate the seismic performance of full-scale reinforced concrete (RC) columns strengthened with high-strength stainless steel wire rope (HSSSWR) meshes reinforced engineering cementitious composite (ECC), considering different axial compression ratios and strengthening schemes. The test results show that the seismic performance of RC columns was greatly improved after being strengthened. Specifically, the failure modes of the columns were changed from flexure-shear failure to compression-flexure failure, and the ductility and energy dissipation capability were significantly improved by 69.6% and 474.6%, respectively. Besides, the HSSSWR meshes reinforced ECC jacket was confirmed to be a more efficient strengthening scheme, compared with strengthening with only ECC or lateral HSSSWRs reinforced ECC. The RC columns still showed good ductility and energy dissipation capacity after being strengthened with HSSSWR meshes reinforced ECC under high axial compression ratios of 0.5 and 0.7. Finally, taking into account the confinement effects of ECC, lateral HSSSWRs, and stirrups, an analytical model used for predicting the envelope curve of strengthened columns with HSSSWR meshes reinforced ECC jackets under cyclic loading was proposed, which was in good agreement with the test results.

Enhancing corrosion resistance of additive manufactured heterogeneous martensite stainless steel by hot isostatic pressing

The effect of hot isostatic pressing (HIP) on microstructure, corrosion resistance and passive film characteristics for heterogeneous martensite stainless steel (MSS) manufactured by laser powder bed fusion (LPBF) was studied. The microstructure was mainly typical original austenite grains and martensite laths and the high content of austenite disappeared after HIP. The average grain size (about 14.09 μm) was larger than that of sample before HIP (about 4.33 μm). When the laser power was 170 W and the scanning speed was 550 mm·s−1, the density of the samples after HIP increased to >99.99%. When the scanning speed increased to 1250 mm·s−1, the density of samples increased from 97.82% to 99.89%. After HIP treatment, the passivation trend of low density (97.8%) samples was more obvious and the pitting potential increased from −44 mVSCE to 179 mVSCE. The pitting potential of high density (99.77%) samples increased from 265 mVSCE to 291 mVSCE and the electrochemical impedance value increased. The sensitivity of the samples to chloride ions significantly decreases after HIP. The donor density for sample before HIP was 2.5546 × 1020 cm−3, which was higher than that of sample after HIP (2.001 × 1020 cm−3). Therefore, the corrosion resistance of LPBF high strength stainless steel was enhanced after HIP.

Additive manufacturing process parameter determination for a new Fe-C-Cu alloy

As a potential replacement for stainless steel alloys commonly used to print parts with laser powder bed fusion, a new Cu precipitation strengthened ferrous alloy, with composition Fe-0.2C-6Cu (wt%), was recently developed. This material is Co- and Ni-free, printable, has mechanical properties comparable to that of high strength stainless steels (approximately 1300 MPa UTS), and is cost-advantaged relative to existing low-alloy steels for additive manufacturing of parts with complex shapes. To gain traction for broader application, optimal laser powder bed fusion (LPBF) processing conditions to produce nearly defect-free parts without compromising mechanical strength are needed. Here, an optimal processing window based upon laser speeds that achieve minimal porosity was quantified via comparisons of measured melt pool penetration, scan speeds, printed material density and laser beam energy density on a commercial LPBF unit operating at 350 W, 80 μm hatch spacing, and 50 μm layer thickness based upon optimal parameters for 17-4PH. The window is 300 to 500 mm/s to achieve >99.8 % dense Fe-0.2C-6Cu (wt%) specimens. Other defects such as burning, spatter, and lack of fusion were also avoided in this window. The window was validated with in-situ synchrotron X-ray imaging that enabled visualization of the vapor cavity, melting, and solidification during a single laser track scan on a miniature powder bed sample. In addition, in-situ infrared imaging provided temperature fields, cooling rate and solidification range, and confirmed minimal printing defects and spatter within the processing window.

Experimental Study on Lap-Spliced Performance of High-Strength Stainless Steel Wire Mesh in Engineering Cementitious Composites.

To investigate the mechanical properties of high-strength stainless steel wire mesh (HSSSWM) in Engineering Cementitious Composites (ECCs) and determine a reasonable lap length, a total of 39 specimens in 13 sets were designed and fabricated by considering the diameter of the steel strand, spacing of the transverse steel strand, and lap length. The lap-spliced performance of the specimens was tested through a pull-out test. The results revealed two failure modes in the lap connection of steel wire mesh in ECCs: pull-out failure and rupture failure. The spacing of the transverse steel strand had little effect on the ultimate pull-out force, but it restricted the slip of the longitudinal steel strand. A positive correlation was found between the spacing of the transverse steel strand and the slip amount of the longitudinal steel strand. With an increase in lap length, the slip amount and 'lap stiffness' to peak load increased, while the ultimate bond strength decreased. Based on the experimental analysis, a calculation formula for lap strength considering the correction coefficient β was established.

Thermodynamic investigation with synergetic method on inner crack growth behavior at very high cycle fatigue regime

This paper presents a thermodynamic characterization method for estimating the internal crack growth rate, which has been a puzzle in very high cycle fatigue research. A theoretical approach of surface temperature is discussed with crack size, initiation site, and time for thin sheet material. Infrared thermography is used to study the inner crack behavior and the heat dissipation phenomenon under 20 kHz vibration loading on high-strength stainless steel. A numerical simulation reveals the consequent temperature elevation on the surfaces by the heat generation at the crack tip and the heat conduction. Ultimately, the internal crack growth rate and final fatigue failure prediction are obtained by combining the calculation of heat dissipation and the observed evolution of the surface temperature field.

Hydrogen embrittlement characteristics in cold-drawn high-strength stainless steel wires

Hydrogen uptake and embrittlement characteristics of a cold-drawn austenitic stainless steel wire were investigated. Slow strain rate testing and fracture surface analysis were applied to determine the hydrogen embrittlement resistance, providing an apparent decrease in resistance to hydrogen embrittlement for a 50% degree of cold deformation. The hydrogen content was assessed by thermal desorption and laser-induced breakdown spectroscopy establishing a correlation between the total absorbed hydrogen and the intensity of near-surface hydrogen. The sub-surface hydrogen content of the hot-rolled specimen was determined to be 791 wt.ppm.

Inclusion Control of 15-5 PH High-strength Stainless Steel through Aluminum Deoxidation

15-5PH high-strength stainless steel is an important alloy used for numerous critical components. Ultra-low oxygen content and inclusion control have become urgent problems that need to be addressed for the broad application of this steel. In this study, we investigate the thermodynamic equilibrium of Al–O and inclusion morphology of 15-5PH stainless steel to understand the basic mechanism behind the results obtained after commercial production of the alloy. The deoxidation behavior of 15-5PH stainless steel depends on the dissolved Al content ([Al%]). When [Al%] <0.001%, mixed Al–Si deoxidation occurs and the deoxidation product is Al2O3–SiO2–MnO–CrOx. When [Al%] ≥0.001%, simple Al deoxidation equilibrium is dominant and the deoxidation product is MgO·Al2O3. The formation of Al2O3–SiO2–MnO–CrOx, low melting point inclusions, and a MgO·Al2O3 interface layer reduces the activity of Al2O3, which is why the calculated results of Al–O thermodynamic equilibrium are higher than the experimental results. The measured results for the Al–O equilibrium demonstrate a relatively good agreement with the calculated values. This proved that the phases formed on the crucible surfaces were in equilibrium with the Al and O contents in the molten steels after holding for 120 min.