热轧S31603/Q370q不锈钢复合板界面特征分析北大核心CSCD

利用热模拟试验研究了热变形参数对热轧S31603/Q370q不锈钢复合板结合界面的显微组织、成分分布、显微硬度、厚比分配的影响。结果表明,S31603/Q370q复合板由不锈钢侧至碳钢侧的组织变化依次为不锈钢基体中的奥氏体组织、渗碳层、富集了大量C、Cr的过渡层、脱碳层和碳钢基体中的铁素体+珠光体组织;过渡层有碳化物形成,其硬度最高,脱碳层为铁素体组织,其硬度最低;随着热变形温度的升高,碳钢的厚比分配增加,不锈钢的厚比分配减小,过渡层硬度峰值降低,脱碳层宽度增加;随着总变形量的增加,碳钢、不锈钢的厚比分配成正比关系增加,过渡层硬度峰值升高,脱碳层宽度变窄。     

等离子喷涂工艺对Fe基非晶合金涂层微观组织结构的影响

通过等离子喷涂技术在Q235基体上制备了一种Fe基非晶涂层。该涂层结构均匀致密,主要含有具有Fe、Cr、B、Si、Ni、Mo和W。通过合理安排实验方案,分别研究了等离子喷涂电压、电流、喷涂距离对涂层的孔隙率、微观组织结构的影响规律。在等离子输入功率一定时,采用较高的喷涂电压将获得孔隙率更低的Fe基涂层;涂层孔隙率分别随等离子输入功率和喷涂距离的增加,均呈先降低后升高的趋势。等离子输入功率为30.25kW时,所制备的Fe基涂层孔隙率为1.19%,显微硬度为717HV0.1。     

湿热海洋大气中SO2污染对Q235B钢腐蚀行为的影响

 以NaCl和NaHSO3为介质,采用干/湿周浸加速腐蚀试验、腐蚀失重分析、XRD、SEM等,研究了湿热海洋大气中SO2对Q235B钢腐蚀行为的影响。结果表明,SO2污染使Q235B钢的腐蚀明显加重。污染前后,Q235B钢的腐蚀过程均遵循幂函数[W＝Atn]的分布规律,腐蚀产物均由非晶和少量Fe3O4、α-FeOOH、β-FeOOH、γ-FeOOH晶体组成,但参数[A、][n]值和晶体数量并不相同。Cl－和SO2在腐蚀过程中具有协同作用,但作用机理不同。Cl－会阻止腐蚀产物吸附,并促使其脱落,进而阻止保护性锈层形成;而SO2在酸化过程中会与钢基体和锈层反应,进而破坏锈层结构,加剧钢的腐蚀。SO2还能抑制β-FeOOH并促进α-FeOOH的生成,进而抑制Cl－的破坏作用并改善锈层的稳定性;但随锈层增厚,SO2的抑制作用减弱,内锈层随之变疏松。     

电力铁塔金具材料碳含量与组织和性能关系探讨

通过对一系列不同成分板式金具工件和5炉不同碳含量实验钢力学性能检测和微观组织分析,研究了碳含量对电力铁塔金具用Q235B钢组织和力学性能的影响。Q235B材料强化作用取决于多种强化方式叠加产生复合作用,随着碳含量增加,铁素体基体中固溶强化作用逐渐增强;第二相即珠光体体积分数增加,其起到的强化作用增强。分析得出:随着碳含量增加,Q235B钢组织中珠光体含量增加,强度升高,韧塑性降低。碳含量(质量分数)小于0.068%时组织中珠光体含量少,材料强度降低。出于金具服役安全性考虑,电力铁塔金具用Q235B钢中碳含量在标准范围内应保证不低于0.068%,保证材料足够的强度。     

等离子喷涂FeCrMoSnPBSiC非晶合金涂层的结构和性能

 将软磁非晶合金FeCrMoSnPBSiC粉末作为喷涂材料,用大气等离子喷涂法在Q235钢板表面制备非晶态合金涂层。结果表明,该非晶态合金涂层组织致密均匀,具有较高的硬度,平均显微硬度为HV01 644,涂层与基材结合强度超过25 MPa,而且涂层具有较高的热稳定性和较好的耐腐蚀性能,起始晶化温度约516 ℃,在5%NaCl溶液中具有钝化作用。     

Roentgenographic Determination of Residual Stresses in Carbonitrided Layers

The aim of the current investigation is to examine the influence of carbonitriding in low-temperature plasma on forming macroresidual stresses in the surface layer of the materials. Particular modes of ion carbonitriding are considered in which layers of different depth and different surface microhardness are obtained. The residual stresses in the α-Fe in carbonitride layers are determined by the method of “sin²Ψ.” The results show that at different modes of ion carbonitriding, residual macrostresses are obtained that have different values and depend on the qualitative characteristics of the formed carbonitrided layers.     

Effect of microstructure on corrosion behavior of low carbon high chrome steel

The two types of microstructure of low carbon and high chromium steel (5Cr) were obtained through the test smelting, rolling and quenching after rolling.Corrosion performance of 5 mass%Cr steel and Q235 steel were researched by means of cyclic wetting and drying corrosion test in 2 mass% NaCl solution.Corrosion behavior and corrosion rust layers were analyzed by OM, SEM, EDS, XRD, cyclic wetting and drying corrosion tester and electrochemical testing. The results show that after the specimens were immersed and etched in 2 mass% NaCl solution for 72h, the different microstructures of 5Cr steel have great influence on the resistance to chloride ion corrosion. B+F+M microstructure of 5Cr steel shows lower corrosion rate than Q235 steel, 5Cr steel with martensite microstructure also shows lower corrosion rate than Q235 steel. Corrosion susceptibility of 5Cr steel with martensite structure is weaker than complex organization.The stratification of chromium oxide, oxyhydroxide, and iron oxide exists in the chromium- containing steel rust layer, in which the Cr enrichment maximum value is 17 mass%, and the lowest is 1 mass%.Lath martensite formed by quenching process makes the corrosion potential rise, ??- FeOOH and ??- FeOOH form. Bainite+ferrite phase and adverse phenomenon of Cr steel may cause the poor corrosion resistance.     

Effect of Pulsed Nitrogen Plasma and Nitrogen Ion Fluxes on the Structure and Mechanical Properties of Vanadium

The effect of powerful pulsed fluxes of nitrogen plasma and nitrogen ions generated in the PF-4 Plasma Focus setup (LPI; energy flux density of plasma pulse was 10⁸–10¹⁰ W/cm²) on the modification of vanadium surface is studied. Melting and ultrafast solidification result in a fine cellular structure (cell size of 100–200 nm) in a thin surface layer in samples. There are irradiation regimes causing directional crack growth after solidification and cooling of the surface layer and the formation of a block microstructure with a block size of several tens of micrometers. The thickness of the melted layer in the samples is 2–4 μm. Cracks propagate to a depth of 5–20 μm. It is established that irradiation by pulsed nitrogen plasma and high-energy nitrogen ions changes the microhardness of the vanadium surface layers. The microhardness increases by a factor of three with the number of plasma pulses and the distance between a sample and the anode of the Plasma Focus (PF) setup. The increase in the microhardness is in agreement with the refinement of coherent scattering regions, the increase in lattice microstrain ε, and the formation of vanadium nitrides. Pulsed fluxes of nitrogen plasma and nitrogen ions decrease the lattice parameter much greater than cold working (rolling) does. The lattice parameter decreases when the total irradiation power is increased (the number of pulses increases or the distance between a sample and the anode of the PF setup decreases). Such changes seem to be caused by the action of the residual macrostresses induced by pulsed plasma irradiation. In addition, X-ray diffraction analysis showed a change in the texture of the surface layer after ion-plasma treatment of coldworked vanadium samples in the PF setup.     

Effect of electropulsing treatment on the mechanical properties of Q235 steel strip

The elctropulsing treatment (EPT) has been successfully applied to the processing of a low carbon Q235 steel strip. Comparing with the conventional heat treatment (CHT), a proper EPT is capable of achieving the similar or even better effect on the mechanical properties of the steel strip. It was found that the optimum combination of the EPT parameters are 180 V in voltage and 500 Hz in frequency (180 V-500 Hz) leading to a combination of tensile strength-elongation of 371 MPa-47.5%. Optical microscopy analyses indicates that the EPT/180 V-500 Hz for Q235 steel strip can accelerate the formation of the completely recrystallized microstructure in which the grain size become relatively finer and more uniform compared to the elongated one formed in the cold-rolled sample. Such phenomenon is consistent with the improvement of the mechanical performance of the Q235 steel sample under the EPT. However, the EPT with inadequate frequency can only result in partial recrystallization of the grains, while the one with an exceed frequency may lead to the apparent grain growth within the sample. Both cases can not produce satisfactory combination of strength and ductility for the steel samples.     

Study of bipolar pulsed nanocrystalline plasma electrolytic carbonitriding on nanostructure of compound layer

Surface hardening of commercially pure titanium by using bipolar pulsed nanocrystalline plasma electrolytic carbonitriding was studied in this investigation. The coating process was performed on triethanolamine-based electrolyte by a cooling bath. The nanostructure of the obtained compound layer was examined with figure analysis of SEM nanographs. The effects of process variables, i.e., triethanolamine concentration, electrical conductivity of electrolyte, applied voltage, and treatment time, have been experimentally studied. Statistical methods were used to achieve the optimum size of nanocrystals. Finally, the contribution percentage of effective factors of pulsed current was revealed and confirmation runs showed the validity of the obtained results. The text was submitted by the authors in English.     

渗硼工艺对汽车用45CrNiMoV热锻模具钢性能的影响

研究了850～950℃3～6 h渗硼处理的汽车发动机曲轴锻造用模具钢的显微硬度、冲击韧性、耐磨性能以及物相组成和微观结构。研究结果表明,925℃渗硼4 h后的样品性能较优,模具钢渗硼层最大HV显微硬度值1712,渗层厚度58.6μm,400℃和24℃冲击韧性值分别为39 J·cm^-2和27 J·cm^-2,90 min摩擦试验后的磨损量6.7 mg。物相组成显示渗硼层主相为Fe₂B,显微结构中可以明显看见渗硼后的渗硼层、过渡层以及基体。     

卷取机夹送辊表面堆焊层组织性能研究

采用埋弧堆焊工艺在Q235B表面堆焊8-10mm的Cr8系列新型熔覆材料,测定其耐磨性和硬度变化,分析熔覆金属的组织形貌和高温工况下的合金元素扩散。研究结果表明,熔覆金属打底层主要是以铁素体为主,伴随着少量的贝氏体。盖面层的焊态组织主要为马氏体和残余奥氏体,伴有少量的回火马氏体,同时在枝晶马氏体间可见少量较小的碳化物。经550℃回火后其盖面层组织为回火马氏体和残余奥氏体,碳化物析出相均布较焊态呈增多趋势。焊态硬度值为530-580HV300,回火后硬度值为720-830HV300,磨损失重是45#淬火钢的0.31倍。在使用3个月后发现在熔覆层表面出现了元素偏移并形成了由Cr2O3、WO等组成的氧化膜,降低了夹送辊的粘钢倾向,提高使用寿命。     

Simultaneous plasma treatment for carburizing and carbonitriding using hollow cathode discharge

Ion carburizing and nitriding are effective processes for saving energy and providing polutionless surface treatment but have the disadvantage of using much electric energy. A cylindric subsidiary cathode was set up around a rod-shaped workpiece with a gap, and hollow cathode discharge for ion carburizing was studied. Thus, simultaneous plasma treatments for ion carburizing and ion car-bonitriding in one workpiece were researched using Cr-Mo steel to save electric treatment power. First, the effects of the gap between the test piece and subsidiary cathode and the pressure of electric discharge gas, including methane gas, on fundamental plasma treatment conditions were experimen-tally researched. It was found that the temperature for ion carburizing in a H₂-N₂-Ar-CH₄ gas mixture was 1123 to 1193 K with a gap of 3 to 5 mm under a gas pressure of 133 to 532 Pa. Next, the test piece was ion carburized with hollow cathode discharge and carbonitrided with normal glow dis-charge simultaneously. The ion-carburized layer was formed in the area covered by the subsidiary cathode. The surface hardness was 800 Hv, the effective case depth was 0.6 mm, and the surface carbon content was 0.75 wt pct. An ion carbonitriding layer was formed in the area without the subsidiary cathode. The surface hardness was 700 Hv and the case depth was 0.1 mm. It is useful to form the different layers of ion carburizing and ion carbonitriding in one treatment process and to give different mechanical and tribological properties on one workpiece simultaneously.     

稀土对等离子束表面冶金涂层组织的影响及热力学分析

 采用直流放电压缩电弧等离子束表面冶金技术,在Q235钢表面制备了添加混合稀土氧化物的铁基合金涂层,研究了稀土对等离子束表面冶金涂层组织的影响。结果表明：添加适量的混合稀土氧化物可有效改善冶金涂层的组织和性能。另外,采用热力学方法,分析了稀土氧化物对冶金层中夹杂物的变质作用。分析结果表明：在冶金熔池中,稀土氧化物(Ce2O3)可以被碳还原为稀土元素,这些稀土元素与氧、硫反应生成稀土硫氧化物,起到脱氧、脱硫和净化熔池的效果,从而抑制冶金层中凝固裂纹的形成。     

Effects of the Process Parameters on the Microstructure and Properties of Nitrided 17-4PH Stainless Steel

The effects of process parameters on the microstructure, microhardness, and dry-sliding wear behavior of plasma nitrided 17-4PH stainless steel were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and wear testing. The results show that a wear-resistant nitrided layer was formed on the surface of direct current plasma nitrided 17-4PH martensitic stainless steel. The microstructure and thickness of the nitrided layer is dependent on the treatment temperature rather than process pressure. XRD indicated that a single α _N phase was formed during nitriding at 623 K (350 °C). When the temperature increased, the α _N phase disappeared and CrN transformed in the nitrided layer. The hardness measurement demonstrated that the hardness of the stainless substrate steel increased from 320 HV_0.1 in the untreated condition increasing to about 1275HV_0.1 after nitriding 623 K (350 °C)/600 pa/4 hours. The extremely high values of the microhardness achieved by the great misfit-induced stress fields associated with the plenty of dislocation group and stacking fault. Dry-sliding wear resistance was improved by DC plasma nitriding. The best wear-resistance performance of a nitrided sample was obtained after nitriding at 673 K (350 °C), when the single α _N-phase was produced and there were no CrN precipitates in the nitrided layer.     

Effect of plasma immersion ion beam processing on the structure–phase state and the properties of the surface layers in titanium nickelide samples

The formation of a microstructure in the surface layers of model samples made of a titanium nickelide–based alloy intended for medical application during plasma immersion processing by silicon ions is studied. Depending on technological conditions, either a silicon coating can be formed or a surface layer can be alloyed. The formed layers have a high microhardness and high adhesion to the base material.     

钢中非金属夹杂物对显微组织的影响

使用金相法对碳素结构钢Q235B钢板的拉伸试样非正常断口进行分析,研究了钢中夹杂物类型和形态以及钢的显微组织。结果表明,Q235B钢板拉伸试样非正常断口及附近部位夹杂物严重,且存在粗大的带状组织,带状铁素体中有明显的非金属夹杂物。粗大带状组织的形成原因是由于铁素体以非金属夹杂物为结晶核心并沿着非金属夹杂物的变形方向生长而形成的。     

回火热处理对460MPa级海洋平台用钢板性能影响研究

采用低碳的成分设计以及轧后调质工艺,开发出满足标准的50 mm厚460 MPa级钢板,并研究了回火温度对组织性能的影响。结果表明：在此成分设计的条件下,调质态的组织为回火贝氏体和M/A,此类组织具有优良的综合力学性能,而且在较宽的回火温度范围内获得良好的性能匹配。     

Microstructure and Thickness of 55 pct Al-Zn-1.6 pct Si-0.2 pct RE Hot-Dip Coatings: Experiment, Thermodynamic, and First-Principles Study

The microstructure and thickness of 55 pct A1-Zn-1.6 pct Si-0.2 pct RE coatings during continuous hot-dip on Q235 steel were investigated in this work. The experimental results revealed that the intermetallic layer was composed of the Fe₂Al₅, FeAl₃, and α-FeAlSi phases. The results of thermodynamic calculations with Pandat software package (CompuTherm, LLC, Madison, WI) indicated that FeAl₃ and α(β)-FeAlSi phase precipitated during the period of temperature cooling, which was consistent with experimental result. Then, the thickness of intermetallic layer was characterized. It was shown that the thickness of intermetallic layer decreased after 0.2 wt pct RE was added. Finally, a first-principles calculation was performed to interpret the effect mechanism of RE on the thickness of intermetallic layer. The results indicated that La substitution in Fe₂Al₅ and FeAl₃ phases could grab electronic charges from Al atoms and weaken the formation of Fe-Al compounds.     

石墨烯对激光熔覆镍基碳化钨涂层组织及性能影响

采用激光熔覆技术在Q235钢基体上制备Ni60A-30%WC-x%石墨烯(质量分数, x=0.0, 0.1, 0.3, 0.5)涂层, 研究石墨烯对激光熔覆镍基碳化钨涂层组织与性能的影响。结果表明, 涂层物相主要由具有γ相结构的Ni-Cr-Fe固溶体、WC、W₂C、Cr₇C₃、Cr₂₃C₆、B₄C等组成; 石墨烯改善了激光熔覆镍基碳化钨涂层的组织, 提高了涂层的硬度和抗摩擦磨损性能; 当石墨烯质量分数为0.3%时, 得到了析出相分布均匀且细小的组织, 涂层具有高硬度、良好的抗裂纹扩展能力和耐磨性。