稀土对1Cr18Ni9钢腐蚀性能及组织状态影响

利用化学法对1Cr18Ni9钢表面扩渗稀土,通过X－射线衍射分析了试样表面的组织状态。结果表明,1Cr18Ni9钢渗入稀土后,表面有CeFe7和LaO新相产生,并引起奥氏体含量降低,铁素体含量增加,改变了试样表面的微观结构。阳极极化曲线的测定结果表明,扩渗稀土后的1Cr18Ni9钢试样耐腐蚀性能超过了稳定化处理的1Cr18Ni9Ti钢水平。     

Cr/Ni当量比对CAP1400核主泵泵壳用奥氏体不锈钢性能的影响

基于热力学分析,设计了2种不同Cr/Ni当量比的CAP1400核主泵泵壳用奥氏体不锈钢,研究了Cr/Ni当量比和固溶处理温度对这类钢中铁素体的含量及其350℃拉伸性能的影响。结果表明,Cr/Ni当量比较大时,泵壳用奥氏体钢中铁素体含量较多,更为粗大;而且350℃时抗拉强度较高,能满足CAP1400核主泵泵壳的力学性能要求。在1100~1200℃不同温度固溶处理后,随着固溶处理温度的提高泵壳用奥氏体不锈钢中铁素体的含量略有提高,但是对350℃时的拉伸强度影响较小。     

C、Cu和Cr对10CrNiCu埋弧焊丝配烧结焊剂焊缝力学性能的影响

针对船用10CrNiCu钢设计了4种不同化学成分的埋弧焊丝,研究了焊丝与烧结焊剂配套使用时C、Cu、Cr元素对焊缝力学性能的影响。结果表明C、Cu可以增加焊缝中针状铁素体的含量,细化晶粒尺寸,从而提高焊缝的低温冲击韧性和拉伸强度,Cr含量增加可以提高焊缝强度,但会降低焊缝的冲击韧性。     

钨含量对新型高铬锰氮双相不锈钢Cr29Mn12Ni2N0.6Wx组织和性能的影响

研究了钨含量对新型高铬锰氮双相不锈钢Cr29Mn12Ni2N0.6Wx(x=1,2,3)显微组织、力学性能和耐腐蚀性能的影响。结果表明:Cr29Mn12Ni2N0.6Wx不锈钢固溶处理后具有典型的铁素体+奥氏体双相组织,铁素体含量在45%~60%范围内;随着钨含量的增加,合金中σ相的析出倾向增强,铁素体含量增加,合金的耐腐蚀性能降低,屈服强度和抗拉强度升高;经1 050℃固溶处理30 min后,该系列双相不锈钢中不再有σ相析出,其屈服强度大于650 MPa,抗拉强度大于900 MPa,断后伸长率大于30%,作为高强度资源节约型超级双相不锈钢具有潜在应用前景。     

Cr和Ni对低碳合金钢微观结构和耐蚀性的影响

为探究Cr和Ni含量对低碳合金钢组织和性能的叠加促进效应，通过SEM、XRD、硬度测试、电化学测试、浸泡试验及XPS测试等方法研究了Cr和Ni含量对低碳合金钢微观结构及其在模拟海水(3.5%NaCl溶液)中耐蚀性的影响。结果表明：同时增加Cr和Ni含量能显著促进钢中形成更多尺寸细小的碳化物Cr₃C₂,进而促进晶粒尺寸减小、马氏体组织细化及增加硬度；同时增加钢中Cr和Ni的含量对钢在模拟海水环境中热力学稳定性、动力学稳定性、抵抗腐蚀损伤能力的提升均大于单独增加Cr或Ni含量的情况；增加钢中Cr的含量能提高NiFe₂O₄、FeO在腐蚀产物中的占比，增加钢中Ni的含量能提高腐蚀产物中FeCr₂O₄、FeO的占比，且同时增加钢中的Cr和Ni含量对提高NiFe₂O₄、FeCr₂O₄、FeO等占比的促进效果高于单独增加Cr或Ni含量的情况；NiFe₂O     

022Cr25Ni7Mo4N双相不锈钢等温处理中的组织演变EI北大核心CSCD

研究经1100℃等温处理2~20 h后022Cr25Ni7Mo4N双相不锈钢的显微组织演变。观察钢中奥氏体晶粒形态变化并对其尺寸进行定量表征,测量铁素体/奥氏体两相中的元素含量变化,并探讨组织演变对实验钢中铁素体相体积分数的各向异性和低温冲击韧性的影响。结果表明:随着保温时间的延长,奥氏体晶粒发生聚集、长大、粗化现象,并伴随显著的晶粒形态变化,a/b值≥4.0时细长棒状晶粒体积分数从近20%骤降至5%以下,a/b值介于1.0~1.9的等轴晶粒体积分数显著上升的同时,尺寸≥20μm的晶粒体积分数快速增加。保温时间的延长使得Mo,Cr元素进一步向铁素体相扩散、富集,并提高铁素体相抗点蚀当量(pitting resistance equivalent number,PREN)值。细长棒状奥氏体晶粒比例的显著下降,是奥氏体体积分数各向异性改善和实验钢低温冲击韧性提高的主要原因。     

Cu对9Ni钢强度和低温韧性的影响

研究了Cu含量(质量分数)对9Ni钢强度和低温韧性的影响,并结合显微组织观察和精细结构分析了含铜9Ni钢的强韧化机理.结果表明,经过淬火+两相区淬火+回火(QLT)处理,Cu含量由0提高到1.5%,9Ni钢的室温屈服强度和抗拉强度分别提高约150和105 MPa;随着Cu含量的提高-196℃低温冲击功呈现先增加后降低的趋势,Cu含量为1.0%时达到最高值157 J,而所有含铜9Ni钢的冲击功均保持在较高的水平。随着Cu含量的增加,钢中二次回火马氏体增加而铁素体减少;颗粒或短杆棒状Cu析出物在基体上析出,组织强化与析出强化共同使钢的强度提高。同时,Cu的加入提高了二次回火马氏体板条边界上的逆转奥氏体含量,并富集于逆转奥氏体中提高其稳定性,从而提高了钢的低温韧性。     

0Cr17Ni4Cu4Nb钢电渣坯裂纹产生原因

0Cr17Ni4Cu4Nb钢电渣锭开坯后，在钢坯角部有裂纹产生。采用宏观观察、化学成分分析、金相检验等方法对该钢坯裂纹产生的原因进行分析。结果表明：开裂钢坯中的碳、氮、镍等元素含量较低，导致材料的铁素体含量较高，铁素体条带宽度较大；铁素体富集区的塑性较差，最终导致钢坯发生开裂。提高钢坯中的碳、氮、镍等元素的含量，可以改善钢坯的表面质量，避免产生裂纹。     

不同热处理条件下30CrMnSiNi2A钢的组织性能研究

为考察热处理工艺对材料性能的影响,对不同回火温度下三种碳含量的30Cr Mn Si Ni2A钢的性能进行实验研究,并分析其组织和断口形貌.研究结果表明:低温回火时30Cr Mn Si Ni2A钢具有较高的强度和硬度,其内部组织为回火马氏体,断口形貌为韧窝断口;当碳含量增大,30Cr Mn Si Ni2A钢的强度也增大;随着回火温度升高,30Cr Mn Si Ni2A钢的强度和硬度逐渐下降,伸长率和断面收缩率却总体呈上升趋势,其组织向索氏体转变,断口形貌变为解理和沿晶断口,回火脆性与其内部形核有关.     

V、N含量和热处理对抗腐蚀油套管组织和性能的影响

研究了不同正火温度和不同V、N含量对1%Cr中碳钢的组织和力学性能的影响,结果表明,V、N含量提高,虽然增加了析出强化作用,但材料强度却随之降低,韧性大幅度提高。在950℃正火温度下较高V、N含量V3钢中的铁素体含量是较低V、N含量的V1钢中铁素体的6倍,而在850℃正火温度下V1钢中的珠光体晶粒尺寸是V3钢的3倍。随着正火温度提高,铁素体和珠光体含量均降低,贝氏体含量增加。因此可以看出增加V、N含量以及降低正火温度都有利于铁素体和珠光体组织转变。通过分析可知,未溶解的V(C,N)会阻碍奥氏体晶粒的粗化,并作为先共析铁素体的形核质点促进了铁素体转变,阻碍了贝氏体的形成,从而获得了具有良好抗腐蚀性能的铁素体+珠光体组织结构,并且使材料强度达到80ksi(552 MPa)。     

Heat treatment and effects of Cr and Ni in low alloy steel

The effects of Cr and Ni on low carbon steel was observed. Undissolved carbide particles refine the austenite grain size. In the presence of nickel, chromium carbide is less effective in austenite grain refinement than chromium carbide in absence of nickel at temperature below 975°C. Nickel does not produce any austenite grain refinement but presence of nickel promotes the formation of acicular ferrites. It was also found that Ni and Cr as chromium carbide also refines the ferrite grain size and morphology. Cr as chromium carbide is more effective in refining ferrite grain size than nickel.     

Residual stress influence on fatigue lifetimes of electroplated AISI 4340 high strength steel

Residual stresses play an important role in the fatigue lives of structural engineering components. In the case of near surface tensile residual stresses, the initiation and propagation phases of fatigue process are accelerated; on the other hand, compressive residual stresses close to the surface may increase fatigue life. In both decorative and functional applications, chromium electroplating results in excellent wear and corrosion resistance. However, it is well known that it reduces the fatigue strength of a component. This is due to high tensile internal stresses and microcrack density. Efforts to improve hard chromium properties have increased in recent years. In this study, the effect of a nickel layer sulphamate process, as simple layer and interlayer, on fatigue strength of hard chromium electroplated AISI 4340 steel hardness – HRc 53, was analysed. The analysis was performed by rotating bending fatigue tests on AISI 4340 steel specimens with the following experimental groups: base material, hard chromium electroplated, sulphamate nickel electroplated, sulphamate nickel interlayer on hard chromium electroplated and electroless nickel interlayer on hard chromium electroplated. Results showed a decrease in fatigue strength in coated specimens and that both nickel plating interlayers were responsible for the increase in fatigue life of AISI 4340 chromium electroplated steel. The shot peening pre-treatment was efficient in reducing fatigue loss in the alternatives studied.     

汽车用高强度TRIP钢组织性能及成形工艺

概述了高强度TRIP钢对汽车轻量化的作用及TRIP钢的显微组织对其性能的影响,探讨了铁素体、贝氏体、残余奥氏体的含量对TRIP钢性能的影响规律,以及设备、模具和成形工艺参数的选择原则。结果表明,TRIP钢中铁素体可以提高铜的塑性,贝氏体可以提高强度和韧性,而当残余奥氏体的体积分数大于8％时,产生TRIP效应,并提高了钢的综合性能;以上组织的获得,应在成形时控制成形设备的能量、栽荷、速度、时间等工艺参数。     

Effects of carbon and chromium on the solidification structure and properties of ferrite–austenite duplex heat-resistant alloy

In order to design a new kind of low-cost high-temperature ferrite–austenite duplex alloy, the effects of carbon and chromium on the alloy solidification structure and properties have been investigated with orthogonal experiments. The addition of carbon promotes strongly the formation of austenite and that of carbides in the alloy solidification structure and refines the alloy grains. With the increase of carbon content, the alloy high temperature strength and oxidation resistance at 1250°C improves at first, but then begins to deteriorate greatly when the carbon content exceeds 0.15%. The addition of chromium facilitates the formation of ferrite in the alloy solidification structure. As the chromium content increases, the alloy rupture strength at 1250°C initially is enhanced, but then reduces rapidly, while the alloy oxidation resistance improves continuously.     

Microsegregation and eutectic ferrite-to-austenite transformation in primary austenite solidified CF-8M weld metals

Solidification and microsegregation studies were performed on alloy CF-8M weld metal which solidified via the primary austenite/eutectic ferrite mode. All of the major alloying elements (chromium, nickel, molybdenum) were observed to segregate to interdendritic areas upon solidification. Electron microprobe analysis revealed a substantial chromium and molybdenum enrichment of the eutectic ferrite relative to the austenite dendrites even in structures water-quenched from the solidus temperature. Scanning transmission electron microscopy/energy dispersive spectrometry (STEM/EDS) profiles taken within the eutectic ferrite phase revealed a similar pattern of major element distribution as has been observed by other investigators in residual primary delta ferrite dendrites. Within the eutectic ferrite, the highest chromium and molybdenum content and the lowest nickel content was found at the eutectic ferrite/austenite boundary. STEM/EDS analyses of in situ water-quenched weld microstructures revealed that compositional modification of the eutectic ferrite had occurred upon cooling from the solidus. In particular, the chromium concentration of the eutectic-ferrite was observed to increase by approximately 3 wt% in the temperature range 1300 to 750°C. In the same temperature range, the nickel content of the eutectic-ferrite decreased by approximately 4 wt % and the molybdenum content increased within the same phase by approximately 1 wt%. The transformation of eutectic ferrite to austenite as the weld metal cools to room temperature is consistent with a volume diffusion-control mechanism.     

The influence of metals and carbides during laser surface modification of low alloy steel

The addition of both elements (Cr and Ni) and carbides (SiC and WC) during laser surface alloying under different processing speeds produced surfaces with both enhanced hardness wear resistance and corrosion properties compared to the base AISI 4340 steel material. These effects were due to the evolution of unique microstructures within the laser-processed region, which includes austenite, ferrite, martensite, Fe- and Si-based carbides and the retention of the original carbides (SiC and WC) in various combinations. The chromium and nickel stabilized the austenite and ferrite but reduced the formation of martensite that is useful to increase the hardness and prevent cracking. Also, the substantial dissociation of the original carbides (SIC and WC) into elemental silicon and tungsten supplemented the stabilization of ferrite and reduction in the hardness. The presence of the undissociated carbides and some martensite formation provided substantial increases in the microhardness. The improvement of both the mechanical properties and corrosion resistance might be self-exclusive due to the reduction of the carbides and the subsequent inability of the matrix to prevent cracking.     

Effect of aluminium on TRIP Fe---Mn---Al alloy steels at room temperature

Fe---Mn---Al alloy steel has undergone many significant developments during the past few years, and it is considered to be a steel of high strength and toughness. Studies and test results have shown that Fe---Mn---Al is a good potential replacement for conventional stainless steels which contain expensive nickel and chromium additions. Recently, it has been found that strain-induced martensitic transformation at room temperature is possible in austenitic Fe---Mn---Al alloy. Further study has shown that the ′ martensite can improve the mechanical properties of these Fe---Mn---Al alloys. However, as the aluminium content increases, the strain-induced phase transformation is inhibited. Moreover, the mechanical properties of these materials are very dependent on the aluminium content.     

Microstructures and Mechanical Properties of Si-AI-Mn TRIP Steel with Niobium

Microstructure consisting of ferrite, bainite and retained austenite can be obtained through intercritical annealing and isothermal treatment in bainite transformation region for low silicon TRIP （transformation induced plasticity） steel containing niobium. Effects of strain rate, Nb content and soaking temperature in bainite region on microstructure and mechanical properties of test steels were investigated. It is shown that as strain rate ranges from 10^-2 to 10^-4 s^-1, the volume fraction of transformed martensite from retained austenite, as well as tensile strength, elongation rate and strength-ductility product, increases. When Nb is added, the volume fraction of retained austenite decreases, but tensile strength and yield strength increase. While Nb content reaches 0.014%, the steel exhibits high elongation and combination of strength and ductility. Higher retained austenite volume fraction and good mechanical properties are obtained in the test steels when the soaking temperature in bainite region is 400℃. The maximum values of tensile strength, total elongation rate and strength-ductility product can reach 739 MPa, 38% and 28082 MPa%, respectively.     

Effect of chromium content on the microstructure and mechanical properties of multipass MMA,low alloy steel weld metal

Effect of chromium content in the range of 0.05–0.91 wt% on the microstructure and mechanical properties of Cr–Ni–Cu low alloy steel weld metal was investigated. All welds were prepared by manual metal arc welding technique in flat position. Microstructure of the welds was examined by optical and scanning electron microscope in both columnar and reheated regions of the weld metal. The results showed increase in acicular ferrite and microphases formed at the expense of primary ferrite and ferrite with second phase with steady refinement of microstructure. According to these microstructural changes, yield and ultimate tensile stresses, Hardness and Charpy V-Notch impact toughness increased, whereas elongation decreased. Increase in Charpy impact value is thought to be due to fine dispersed spheroidized dark microphases at high chromium contents.     

Microstructures and Mechanical Properties of Si-Al-Mn TRIP Steel with Niobium

Microstructure consisting of ferrite, bainite and retained austenite can be obtained through intercritical annealing and isothermal treatment in bainite transformation region for low silicon TRIP (transformation induced plasticity) steel containing niobium. Effects of strain rate, Nb content and soaking temperature in bainite region on microstructure and mechanical properties of test steels were investigated. It is shown that as strain rate ranges from 10-2 to 10-4 s-1, the volume fraction of transformed martensite from retained austenite,as well as tensile strength, elongation rate and strength-ductility product, increases. When Nb is added, the volume fraction of retained austenite decreases, but tensile strength and yield strength increase. While Nb content reaches 0.014%, the steel exhibits high elongation and combination of strength and ductility. Higher retained austenite volume fraction and good mechanical properties are obtained in the test steels when the soaking temperature in bainite region is 400℃. The maximum values of tensile strength, total elongation rate and strength-ductility product can reach 739 MPa, 38% and 28082 MPa%, respectively.