Cr12MoV模具钢渗氮层服役过程中不同磨损阶段的摩擦学特性

目的 分析经渗氮处理后Cr12MoV模具钢的显微结构,以及不同取样厚度处渗氮层的摩擦学特性,了解渗氮处理对Cr12MoV模具钢耐磨性的影响,为服役过程中不同磨损阶段渗氮层的磨损行为提供理论依据。方法 采用气体渗氮法对Cr12MoV模具钢进行恒温渗氮处理,研究渗氮处理对Cr12MoV模具钢显微结构的影响,以及不同取样厚度处渗氮层的磨损行为,并分析不同取样厚度处渗氮层的磨损机理。结果 经渗氮处理后Cr12MoV模具钢的表面会形成一层厚度约为120 μm的致密渗氮层,材料的表面硬度从3.65 GPa提高至12 GPa,磨痕深度从3.5 μm降至0.35 μm。随着取样厚度的增加,试样的磨损量会逐渐增加,但均远低于未渗氮试样,其中渗氮层的最大磨损量约为120 μm³,为基体材料磨损量的1/10;渗氮影响层的最大磨损量约为330 μm³,为基体材料的1/3,可见采用气体渗氮处理可显著增强Cr12MoV模具钢的耐磨性。此外,在磨损过程中Cr12MoV模具钢的表面磨损较严重,出现了大块撕裂损伤,主导磨损机理为疲劳磨损;经渗氮处理后试样表面的损伤较轻微,主导磨损机制为磨粒磨损。随着取样厚度的增加,试样表面的磨损现象逐渐加剧,磨损机制由磨粒磨损逐渐转变为疲劳磨损。结论 渗氮处理可以在Cr12MoV模具钢的表面生成一层致密的渗氮层,渗氮层的磨损量会随着取样厚度的增加先减少后持续增加,说明在服役过程中渗氮层的耐磨性呈先增强后减弱的趋势。     

钒对Cr12Mo模具钢渗氮层及其摩擦学行为的影响

在Cr12Mo和Cr12MoV模具钢表面进行气体渗氮处理,对比分析了V对Cr12Mo模具钢渗氮层显微结构及其摩擦学行为的影响。结果表明,气体渗氮后两种模具钢的表面均制备出深度约120 μm的渗氮层,由表及里依次为渗氮层、扩散层和基体;V提高了模具钢的耐磨性,Cr12MoV表现出较好的耐磨效果;相比V对模具钢基体和扩散层硬度的提升而言,V对渗氮层最大硬度值附近区域的硬度提升幅度更为明显;V对两种模具钢渗氮层耐磨性的影响并不明显,但V的主要贡献在于促进了渗氮时N的有效渗入,大大提高了渗氮层与扩散层间的界面结合力,避免了渗氮层与扩散层间的开裂,促使磨损机制由疲劳磨损转变为黏着磨损,进一步提高了渗氮层的服役寿命。     

表面机械研磨处理对H13钢离子渗氮行为的影响

采用SEM、TEM和显微硬度计等研究了H13钢表面经机械研磨处理后520℃离子渗氮行为.结果表明,经过机械研磨(SMA)处理后H13钢表层形成了一定厚度的变形层,该变形层的晶粒尺寸10～20 nm,表面硬度约800 HV0.2.在直流脉冲渗氮炉中经520℃离子渗氮5 h后,未SMA处理和经SMA处理后的渗氮层厚度分别为65 μm和115 μm,表明机械研磨处理对H13钢离子渗氮具有明显的催渗作用.     

Cr12MoV钢的等离子渗氮的优化

Cr12MoV冷作模具钢的表面改性技术研究一直受到关注。本文采用双辉等离子体渗金属设备研究了等离子渗氮的工艺参数对渗氮层质量的影响。通过优化工艺参数实现了对Cr12MoV钢可靠渗氮,炉压500 Pa、渗氮温度500～550℃和保温4 h,渗层表面显微硬度最高达到1100 HV、渗层深度为0.15 mm。本研究拓展了双辉等离子渗金属设备的应用范围。     

温度对AISI304奥氏体不锈钢离子渗氮的影响

对AISI304奥氏体不锈钢进行脉冲电流辉光离子渗氮处理,在不同处理温度(480 ℃、520 ℃、580 ℃)下渗氮8 h后,获得了一定厚度的渗氮层.通过对渗层进行金相分析和硬度测试表明,随着渗氮温度升高,渗层厚度增大,显微硬度先增大后减小.综合温度对渗层厚度与显微硬度的影响,AISI304奥氏体不锈钢卡套辉光离子渗氮温度可采用520 ℃,渗氮后渗层厚度为90 μm,显微硬度为1317 HV0.1.     

低碳钢渗铝加离子渗氮的表面硬化处理

为了在低碳钢表面得到高的渗氮层表面硬度 ,对含碳量为 0 2 %的低碳钢和工业纯铁进行了粉末渗铝加离子渗氮的复合化学热处理试验。具体工艺为 :试样经 95 0℃× 6h粉末渗铝后 ,再进行 5 6 0℃× 8h的离子渗氮。结果表明 ,渗铝后可得到 1 0 0 μm的渗铝层 ,其硬度为 (30 0± 1 0 )HV0 1 ,约为铁素体基体硬度的 2倍 ;渗氮后在表面形成了 2 0 μm～ 4 0 μm厚、硬度高达 (1 30 0± 5 0 )HV0 1的硬化层。X射线衍射分析表明 ,渗氮处理后在表面形成的氮化铝相与表面的高硬度有关     

退氮处理对SDHS2模具钢渗氮层组织与性能的影响

采用光学显微镜和显微硬度仪对比研究了离子渗氮的SDHS2模具钢退氮处理前后渗氮层的组织和性能。结果表明:通过离子渗氮处理得到的渗层深度约230μm,渗层表面硬度达1 000 HV0. 3以上,渗层组织致密,与基体结合良好;分别经530和550℃退氮处理8、12、16 h后,渗氮层的硬度均大幅度降低。但随着渗氮时间的延长,渗层硬度随之提高;退氮温度的升高也会导致基体硬度的大幅度下降。综合比较得出,SDHS2模具钢退氮处理的最佳工艺为:退氮温度530℃、退氮时间8 h。在保证基体硬度满足要求的条件下,退氮处理可使表面硬度由处理前的1 000 HV0. 3以上降低至780 HV0. 3左右。     

Q235钢离子渗铬及渗氮复合处理的耐磨性

利用针状铬丝在Q235钢表面进行1000 ℃×4 h等离子渗铬,对渗铬试样分别进行(480、520、560 ℃)×6 h的离子渗氮处理.对经过渗铬和离子渗氮处理的试样进行磨粒磨损耐磨性试验.结果表明,Q235钢渗铬后表面铬含量为22wt%,渗层厚度为50 μm.渗铬层经渗氮处理形成了含铬氮化物(CrN、Cr2N)及少量含铬碳化物(Cr23C6)组成的表面强化层,表面显微硬度最高达1500 HV0.1.磨粒磨损试验表明,与未处理Q235 试样比较,渗铬并经过480、520、560 ℃离子渗氮处理的试样耐磨性分别提高了1.50、3.05和1.44倍;520 ℃离子渗氮试样较T10钢淬火+低温回火试样及3Cr13离子渗氮试样分别提高了2.20倍和2.73倍.     

温度对Cr12MOV钢等离子S-N-C复合共渗渗层组织的影响

对冷作模具钢Cr12MoV在等离子渗氮的基础上进行250℃,450℃,520℃的S—C—N复合共渗,在获得具有良好支撑作用的高硬度表面基础上,形成一定厚度的硫化物层。用光学显微镜、扫描电子显微镜、能谱仪等方法对渗层表面组织及截面形貌进行了分析,结果表明,随着温度的升高,渗硫层变厚,硫化物颗粒变大;520℃等离子复合共渗3h可得到良好组织结构的表面处理层。     

强力喷丸对4Cr5MoSiVl钢离子渗氮的影响

对调质后的4Cr5MoSiVl钢进行强力喷丸处理,将喷丸处理后的试样在520℃下离子渗氮1 h。采用光学显微镜、透射电子显微镜、显微硬度仪和X射线衍射仪对比分析了喷丸和未喷丸试样亚表层的显微组织、渗层深度、硬度分布及表面物相组成。结果表明,在520℃离子渗氮l h的情况下,喷丸的催渗效果十分明显,喷丸后渗氮层深度从31.6μm增至52.5μm,表面层显微硬度从986 HV增加到1084 HV。喷丸试样的渗氮层与未喷丸试样相比,表面物相及含量都有不同。     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis     

Preface

<正>We are pleased to present this Special Issue of Transactions of Nonferrous Metals Society of China containing selected papers from the First Asian Conference on Aluminum Alloys(ACAA-2013),held in Beijing,China,13–17 October 2013.This conference has been initiated,with approval of     

Information for Contributors

The Transactions of Nonferrous Metals Society of China, founded in 1991 and sponsored by The Nonferrous Metals Society of China, is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology, including mineral processing, extraction metallurgy, metallic materials and heat treatments, metal working, physical metallurgy, powder metallurgy, with the emphasis on fundamental science. It is the unique preeminent publication in English for scientists, engineers, under/post-graduates on the field of nonferrous metals industry. This journal is covered by many famous abstract/index systems and databases such as SCI Expanded, Ei Compendex Plus, 1NSPEC, CA, METADEX, AJ and JICST.     

INTRODUCTION TO PATENTS

The invention provides a method of making a mold which can reduce SOx generation rate while preventing decrease in hardening rate in the case of using sulfuric acid for a hardener composition. The method has a mixture step in which fire-resistant particles, a hardener composition and a binder composition are mixed to obtain a composition for a mold. The hardener composition contains sulfuric acid. In the mixture step, sodium carbonate is added. A molar ratio of the sulfuric acid to the sodium carbonate is 0.5 or more and 4.0 or less.     

China Foundry Week 2014

China Foundry Week, hosted by the Foundry Institution of Chinese Mechanical Engineering Society （FICMES） each year, is a large academic event in China. It is one of the ten high-impact activities sponsored by the Chinese Mechanical Engineering Society.     

17th Conference of Hydrodynamic and Electromechanical Control Engineering Call for papers

正1.Contents In order to promote the academic exchanges and technical communication of the research in the field of fluid power transmission and control,fluid control engineering specialized committee of the Chinese Society of Theoretical and Applied Mechanics will hold the 17th Conference of Hydrodynamic and Electromechanical Control Engineering on July 27-29,2014 in Tibet,Lhasa city.     

Formulas of Tension of Continuous Rolling Process

The development of computer controlled continuous rolling process calls for a mathematical expression that can express the inequality condition of "constant flow". Tension is the link of the continuous rolling process. From the condition of dynamic equilibrium, a differential equation of tension is given out. On the basis of the physical rules established from the industrial practice and experimental studies, the law of volume constancy, the linear relation of forward slip and tension, the state equation of continuous rolling, the formula of dynamic tension, and the formula of static tension have been obtained. These formulae reflect the functional relations between tensions, thickness, roll velocity, and time in the continuous rolling process. It is implied that the continuous rolling process is a gradually steady, controllable, and measurable dynamic system. An assumption of predicting the thickness of a steel plate using these tension formulae is also put forward.