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Effect of heat treatment on microstructure and mechanical properties of Ti-containing low alloy martensitic wear-resistant steel

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China Foundry 2023年第4期20卷 329-338页

作者： Kai Lan Wang Ding yi-tao yang School of Materials Science and Engineering Shanghai UniversityShanghai 200444China

Effects of quenching temperature and cooling conditions(water cooling and 10%NaCl cooling)on microstructure and mechanical properties of a 0.2%Ti low alloy martensitic wear-resistant steel used for die casting ejector plate were *** results show that lath martensite can be obtained after austenitizing in the range of 860-980℃and then water *** an increase in austenitizing temperature,the precipitate content gradually *** precipitates are mainly composed of TiC and Ti4C2S2,and their total content is between 1.15wt.%and 1.64wt.%.The precipitate phase concentration by water-cooling is higher than that by10%NaCl cooling due to the lower cooling rate of water *** the austeniting temperature increases,the hardness and tensile strength of both water cooled and 10%NaCl cooled steels firstly increase and then *** experimental steel exhibits the best comprehensive mechanical properties after being austenitized at 900℃,cooled by 10%NaCl,and then tempered at 200℃.Its hardness,ultimate tensile strength,and wear rate reach551.4 HBW,1,438.2 MPa,and 0.48×10^(-2)mg·m^(-1),respectively.

关键词： low alloy wear-resistant steel quenching temperature cooling condition precipitate retained austenite wear resistance

Microstructure and properties evolution of Nb-bearing medium Cr wear-resistant cast steel during heat treatment

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Journal of Iron and Steel Research International 2021年第6期28卷 739-751页

作者： Jia-cheng Zhang Tuo Zhang yi-tao yang School of Materials Science and Engineering Shanghai UniversityShanghai 200444China

The effect of quenching temperature and cooling conditions on the microstructure and mechanical properties of a 0.2%Nb medium chromium wear-resistant cast steel was *** microstructure,carbides and volume fraction of retained austenite were characterized using the optical microscope,scanning electron microscope,transmission electron microscope and X-ray *** influence of heat treatment on hardness,impact toughness and tensile properties of test steel was *** can be observed that lath martensite can be obtained under the condition of air cooling and oil cooling upon austenitizing in the range of 900–1020℃.Total carbide content of 0.2–1.1 wt.%under air cooling is more than that under oil cooling due to the lower cooling ***6C5,M23C6 and M7C3 were found at lower austenitizing temperature,of which niobium carbide mostly located at grain boundaries,while chromium carbides were uniformly distributed in the matrix with the size of 20–50 *** chromium carbides are basically dissolved into the matrix in test steel austenitized at 1020°***,the negligible growth of prior austenite grain size is *** austenitized at 1020℃ and cooled in air+tempered at 200℃ has a best combination of hardness,plasticity and tensile strength due to fine grain size and more amount of retained *** this condition,the hardness is 58 HRC,the impact toughness is 22.92 J/cm^(2),and the tensile strength is 1136.9 MPa.

关键词： Wear-resistant steel Quenching temperature Cooling condition Carbide Retained austenite Strengthening Toughening

Effect of yttrium addition on microstructure, mechanical and corrosion properties of 20Cr13 martensitic stainless steel

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Journal of Iron and Steel Research International 2020年第4期27卷 451-460页

作者： Qi-yu Zang yang-fan Jin Tuo Zhang yi-tao yang School of Materials Science and Engineering Shanghai UniversityShanghai 200444China

The effects of rare-earth yttrium(Y)element on the microstructure,mechanical properties and corrosion properties of 20Cr13 martensitic stainless steel were investigated by optical microscopy,scanning electron microscopy and tensile *** experiments were carried out to study the effect of rare-earth element Y addition on corrosion *** results showed that the addition of 0.02 wt.%rare-earth yttrium to martensitic stainless steel could affect the microstructure transformation,and Ac3 temperature was obviously *** the stainless steel after heat treatment,there were more pro-eutectoid ferrite in the steel with 0.02 wt.%*** mechanical test results showed that the addition of 0.02 wt.%yttrium could significantly improve the tensile strength and elongation of the steel,which was related to the influence of yttrium element on inclusions in the test *** the quenching temperature of 0.02 wt.%yttrium steel increasing,the content of the ferrite in steel was affected and the corrosion resistance was remarkably improved.

关键词： Yttrium Martensitic stainless steel Mechanical property Microstructural characterization Corrosion

Experimental study and cellular automata simulation of corrosion behavior of ferritic stainless steel in molten aluminum

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Journal of Iron and Steel Research International 2022年第9期29卷 1485-1494页

作者： Ji-yin Long Tian-tian Zhao Mei-yi Yuan yi-tao yang School of Materials Science and Engineering Shanghai UniversityShanghai 200444China

The corrosion behavior of feritic stainless steel(446)after being immersed in molten Al alloy at 750℃ for 1,2,4,and 8 h has been investigated experimentally and *** microstructure and composition distribution at the corrosion interface were characterized using the optical microscope,scanning electron microscope,and energy dispersive *** results showed that Cr and Si synergistically delay the progress of corrosion at the interface of the intermetallic compounds(IMC).In the early stage of corrosion,Si element was enriched at the interface of IMC1 and IMC2,and the diffusion channels of Al element were occupied by ***,as the corrosion progresses,Cr and Si gradually gather to form a band-like structure and coarsen,causing their hindering effect to be *** the corrosion time increases,the banded structure was further aggregated and coarsened,and the inhibitory effect of Cr and Si elements on corrosion was strongly *** addition,based on the cellular automata dynamics model of reaction-diffusion,the corrosion process of ferritic stainless steel in aluminum alloy melts was *** is demonstrated that if there is no stabilizing effect of Cr element,the thickness of IMC will be doubled.

关键词： Stainless steel Molten Al alloy Intermetallic Diffusion-Cellular automata

Behavior of Nb influence on structure and properties of 30Cr13 cast martensitic stainless steel

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Journal of Iron and Steel Research International 2019年第5期26卷 462-471页

作者： yang-fan Jin Tuo Zhang Qi-yu Zang yi-tao yang School of Materials Science and Engineering Shanghai University Shanghai 200444 China

The microstructure, mechanical properties and corrosion resistance of 30Cr13 martensitic stainless steel (MSS) with different Nb contents were investigated by using the optical microscope, scanning electron microscope, X-ray diffractometer, HRC hardness measurement apparatus and tensile testing machine. Nb was found to retard the formation of austenite and promote the precipitation of carbides by calculating. The results showed that the addition of 0.2 wt.% Nb elements could improve the strength and corrosion resistance of 30Cr13 martensitic stainless steels while the reduction in toughness was less because of the inhibited effect on Cr-rich carbides precipitation by Nb addition. Specially, M23C6-type carbides almost disappeared in 0.6Nb-MSS. Moreover, the main existent form of Nb element was NbC and the strong carbide-forming ability of Nb element increased the quantity of carbides with the morphology changing from sphericaltype to chain-type. 0.2Nb-MSS shows excellent strength, adequate toughness and sufficient corrosion resistance for the application.

关键词： Niobium addition Martensitic stainless steel Microstructure Mechanical property Corrosion resistance

Effect of Precipitation on Intergranular Corrosion Resistance of 430 Ferritic Stainless Steel

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Journal of Iron and Steel Research International 2015年第11期22卷 1062-1068页

作者： Xun-zeng HUANG Dan WANG yi-tao yang School of Materials Science and Engineering Shanghai University

With Nb-Ti-stabilized 430 ferritic stainless steel（NTS430FSS） and SUS 430 ferritic stainless steel（SUS430FSS） as experimental materials, the influence of precipitation on intergranular corrosion resistance was investigated. A series of aging treatment were carried out. The free-exposure corrosion test and double loop electrochemical potentiokinetic reactivation（DL-EPR） test with a scan rate of 1.67 m V/s at 26 °C were applied to evaluate the intergranular corrosion（IGC） resistance. Metallographic observation, scanning electron microscope（SEM）, transmission electron microscope（TEM） with energy dispersive spectroscopy（EDS） and X-ray diffraction（XRD） analysis were conducted. The results show that IGC occurred in SUS430 FSS aged above 700 °C, while it occurred in NTS430 FSS as the temperature was improved to 1 050 °C. The critical degree of sensitization Ir/Ia reaches 0.305 in SUS430 FSS, which is higher than that of NTS430 FSS, i.e. 0.010, aged at 950 °C for 2 h. The TEM, EDS and XRD results show that a large amount of Cr23C6 precipitates with size of 60 nm×22 nm are located at the SUS430 FSS grain boundaries as chains. With the addition of Nb and Ti and reduction of C, the amount of precipitates reduces significantly in NTS430 FSS. A majority of Cr23C6 were replaced by Ti C and Nb C. Only a small amount of spherical Ti C（R=186 nm） and square Ti N（312 nm×192 nm） with Nb and Cr adsorbed are left along grain boundaries. Due to the dual stabilization of Nb and Ti, the precipitation of Cr23C6 is restrained, the chromium depleted region is avoided and accordingly the resistance to the intergranular corrosion is improved.

关键词： 430 ferritic stainless steel intergranular corrosion double-loop electrochemical potentiokinetic reactivation carbonitride extraction precipitation

Fitting function representation for strain fields and its application to the optimizing process

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International Journal of Minerals,Metallurgy and Materials 2014年第6期21卷 556-562页

作者： Kun Chen Ke-jia Liu Li-qun Wei yi-tao yang School of Materials Science and Engineering Shanghai Institute of Technology School of Materials Science and Engineering Shanghai University

A fitted function method to describe the strain fields during forging was discussed to optimize the homogeneous distribution of strain in the axial forging zones during successive stretching. The results are verified by experiment and numerical simulation, and the devia-tions between experiment and simulation are less than 24%. Therefore, the fitted function method can be applied to optimize the stretching process for large forgings. The optimal value of feed determined by the analytic method ensures that the degree of inhomogeneity in strain in the axial ingot zone is less than 6%. This work provides a mathematic model to optimize technological parameters in stretch forging of large ingots.

关键词： forging strain fitting fimcfion representation optimization

Microstructure evolution and corrosion behavior of Nb-alloyed cast heat-resistant steel during different aging treatments

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Journal of Iron and Steel Research International 2020年第12期27卷 1456-1465页

作者： Lv-dan Teng Tian-tian Zhao Teng-fei Cheng yi-tao yang School of Materials Science and Engineering Shanghai UniversityShanghai 200444China

The microstructure evolution of heat-resistant cast stainless steels aged at 600, 700, 800 and 900 ℃ for 2 h was investigated by scanning electron microscopy and X-ray diffraction. Potentiodynamic polarization curves were applied to study the effects of Nb addition and aging temperature on corrosion resistance. The results demonstrated that eutectoid decomposition of the ferritic phase (δ → σ + γ2) was observed at 700-900 ℃. The content of σ-phase first increased and then decreased in the steels, where the maximum content was obtained at 800 ℃, indicating that the highest hardness occurred at 800 ℃ accordingly. The hardness of Nb-containing steels was significantly higher than that of Nb-free steels. The corrosion resistance of heatresistant cast steels in various aging temperatures was different due to the formation of σ-phase. Both Cr-rich carbides and σ-phase were harmful to the corrosion resistance, while Cr-rich carbides were the main factor. Nb-containing heat-resistant cast steels exhibited superior corrosion resistance, as Cr-rich carbides were reduced and the corrosion products of Nb-rich slowed down the formation of steady-state pits.

关键词： Nb addition Aging temperature σ-phase Polarization Pitting corrosion

Effect of Si on high temperature oxidation of 30Cr13 stainless steel

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Journal of Iron and Steel Research International 2017年第5期24卷 561-568页

作者： Hong-huan Mao Xing Qi Jing Cao Li-cong An yi-tao yang School of Materials Science and Engineering Shanghai University Shanghai 200072 China

The effect of Si on the high temperature oxidation behavior of the 30Cr13 martensitic stainless steels was investigated. The underlying mechanism was further discussed by oxidation kinetics curves, scanning electron microscopy （SEM） and X-ray diffraction （XRD） analysis. It was ob- served that the addition of Si can significantly reduce the mass gain per unit area and the oxidation rate of the experimental steels. With the increase of Si content, the film surface composed of the wheat-like oxides turned into the small granular oxides after oxidation for 120 h. The SiO_2 film formed on the metal substrate inhibited the outward diffusion of the metal cation and the inward diffusion of the oxygen anion; thus, the high temperature oxidation resistance was enhanced.

关键词： Metallic material Martensitic stainless steel High temperature oxidation Oxidation kinetics