前驱体对含Cu低碳钢I&Q&P处理后组织性能的影响

采用IQP工艺和EPMA、SEM和XRD等手段,研究了3种前驱体对含Cu低碳钢残余奥氏体含量及力学性能的影响。结果表明,双相区保温初期试验钢奥氏体长大由C配分控制,后期由合金元素Mn、Cu配分控制;双相区保温奥氏体化后,双相区配分后形成弥散分布的局部高浓度Mn、Cu区域仍保留富集效果,在随后的淬火-碳配分阶段易于形成残余奥氏体。经IQP处理后,前驱体为P+F的钢室温组织中马氏体板条较粗,原始奥氏体晶界并不明显;前驱体为F+M钢得到的马氏体板条有序细密;前驱体为M的钢室温组织中马氏体板条更加细密。其中,前驱体组织为M的钢中残余奥氏体量最高,延伸率为24.1%,强塑积可达25 338 MPa·%,综合性能最好。     

合金元素在淬火配分钢中的应用研究进展

淬火配分钢作为第三代先进高强汽车钢候选材料之一,兼备低成本、高强度、高塑性等突出优点。与第一代、第二代先进高强钢相比,淬火配分钢更加符合现代汽车轻量化、绿色化与安全化的发展趋势,可用于制造保险杠、碰撞梁与A/B/C柱等强度高且成型复杂的冲压件。其中,合金元素是淬火配分钢的研发基础,近年来通过发挥钢材内合金元素的作用,遵循"多相"、"亚稳"、"多尺度"组织调控理念,使得淬火配分钢在综合性能方面取得了长足的进展。但由于淬火配分钢强度较高(800～1 500 MPa),目前仅宝钢、鞍钢、唐钢等少数国内钢铁企业具备生产能力。受Mn-Si系TRIP钢以及高Si无碳空冷贝氏体钢研发的启示,Speer J G基于高碳/中碳含硅钢实验结果以及热力学与动力学模拟,较全面地揭示了淬火-配分的概念。其难点在于淬火温度及配分时间的选取,即在保证强度的前提下使C配分最大化,以获得最佳马氏体/奥氏体复相组织配比,由此吸引众多研究者对淬火与配分工艺参数进行不断的探索,并发现在配分过程中将不可避免地引起碳化物析出、奥氏体分解,无法实现理想情况下的C完全配分到奥氏体中,导致残余奥氏体含量仅10%左右,限制延伸率进一步增加。若持续增添C又会恶化焊接性能。为解决这一矛盾,国内外研究者相继提出利用C、Mn等合金元素协同配分稳定奥氏体的想法,其中合金元素配分行为及促进其配分的途径成为目前淬火配分钢中奥氏体稳定化的研究焦点。研究者们利用3D-APT或EPMA技术对不同合金元素在铁素体、奥氏体、渗碳体间的配分行为进行表征并取得了丰硕的成果。钢中主流合金元素C、Mn、Si/Al、Cu/Ni在各相间化学势梯度的驱动下进行扩散,其中C、Mn、Cu/Ni原子偏向奥氏体一侧扩散,起稳定奥氏体的作用,而Si/Al向铁素体中配分,抑制渗碳体析出。此外,大量实验也证实了两相区加热及变形可强化合金元素的配分行为。本文简单介绍了淬火配分工艺的特点,阐述了淬火配分钢的增塑机理;并分析了不同合金元素在淬火配分钢中的作用,重点论述了不同合金元素的配分行为;同时根据合金元素的配分特点,详细指出了两种促进合金元素配分的主要途径;最后对合金元素在淬火配分钢中应用的前景进行了展望,为淬火配分钢的产业化发展奠定基础。     

多元合金团簇构型优化的研究

为了研究多元合金基体的稳定性,探讨了获得多元合金团簇平衡几何构型的途径,根据随机行走思想编写了多元合金构型优化的计算程序,并铸造了3种合金样品,其基体成分分别为Fe7Cr0.68Mn2.0V1.47Ni1.37Si0.7C,Fe8Cr0.74Mn2.3V1.45Ni1.55Si0.5C,Fe7Cr0.80Mn1.86V1.47Ni1.47Si0.8C,研究了这3种Fe基多元合金奥氏体基体的稳定性及平衡几何构型.计算结果表明:合金1的奥氏体基体最稳定,合金3的奥氏体基体最不稳定,最容易转变成马氏体,与X射线衍射结果一致.     

低碳硅锰钢I&Q&P处理中C,Mn元素配分综合作用EI北大核心CSCD

采用EMPA,SEM和XRD等手段,研究低碳硅锰钢在双相区保温淬火(I&Q)、双相区保温+奥氏体化+盐浴配分(I&Q&P)和奥氏体化+盐浴配分(Q&P)工艺中的C,Mn元素配分行为及对残余奥氏体的综合作用。结果表明:经I&Q工艺处理后,得到马氏体、铁素体加少量残余奥氏体混合组织,C,Mn在马氏体中出现了富集,并且C富集程度高于Mn;经I&Q&P工艺处理后,C,Mn在板条马氏体中呈现不均匀分布,C的局部富集现象更明显,按C,Mn含量的不同,马氏体可分为"高C高Mn"、"高C低Mn"和"低C低Mn"3种;相比较Q&P工艺中只有C配分作用稳定残余奥氏体,I&Q&P工艺在C,Mn配分综合作用下,能得到更多的残余奥氏体。     

奥氏体化合金元素Mn和Ni对FV520B焊缝组织与力学性能的影响EI北大核心CSCD

采用金相观察及扫描电镜(SEM)等研究了奥氏体化合金元素Mn和Ni对FV520B马氏体不锈钢的焊缝组织及力学性能的影响。结果表明,FV520B不锈钢的焊缝组织以回火马氏体为主,随着合金元素增加,焊缝组织变得更加细小。Mn,Ni元素能够有效提高焊缝中奥氏体的含量。合金元素对焊缝强度的影响较小,但当同时添加Mn,Ni元素时,焊缝抗拉强度和屈服强度得到提高。Mn,Ni元素能够通过提高焊缝奥氏体量改善焊缝的冲击韧度。相对于Mn元素,Ni元素提高焊缝韧性的效果更好。     

添加Si对马氏体不锈钢淬火-配分组织和性能的影响

为改善马氏体不锈钢的强塑性和耐蚀性,设计制备了Si含量不同的两种氮合金化马氏体不锈钢10Cr13N钢和10Cr13Si2N钢.对实验钢进行了改变配分时间但恒定淬火终止温度和配分温度的淬火-配分处理,从显微组织和力学性能的变化规律探究添加Si元素的作用与机理.结果表明:实验钢淬火-配分处理后得到板条马氏体加残余奥氏体为主的复相组织,其强塑性配合显著高于淬火-回火状态.随配分时间的延长,两种钢组织中残余奥氏体的含量呈现先上升后下降的极值规律,这一变化对强度影响不大,但对伸长率影响较为显著.增加钢中的Si含量,有利于抑制马氏体中碳氮化物析出并提高残余奥氏体含量和稳定性,在使钢的冲击韧性略微下降的同时可显著改善钢的变形能力.     

配分时间对Q&P钢力学性能及显微组织的影响

设计了一种中碳中锰QP(Quenching and partitioning)钢,基于热力学平衡理论计算分析了其相变过程,通过扫描电镜(SEM)、背散射电子衍射(EBSD)和透射电镜(TEM)研究了实验钢经不同热处理后的微观组织,测试了其力学性能,并采用X射线衍射仪(XRD)进一步分析了拉伸断裂前后残留奥氏体含量的演变规律。结果表明:室温下实验钢微观组织为板条状马氏体和弥散分布的残留奥氏体;残留奥氏体主要存在于马氏体板条之间和原始奥氏体晶界处;随配分时间延长,抗拉强度逐渐降低,延伸率呈现升高趋势;试样拉断后,断口处残留奥氏体含量在3.5%~4.5%之间,明显低于拉伸前的含量(6.94%~10.78%),说明大部分残留奥氏体在拉伸过程中发生了TRIP效应,提高了实验钢的塑性。     

30Cr3Si2Mn2NiNb钢中未溶相的热力学计算及分析

采用Thermo-Calc热力学软件模拟了30Cr3Si2Mn2NiNb钢奥氏体化时平衡相的演化规律以及非平衡态相的演化规律,研究了合金元素C,Mo,Nb和V对实验钢中未溶相的影响.通过SEM,XRD对30Cr3Si2Mn2NiNb钢淬火态组织进行实验观察及分析.结果表明:常规奥氏体化处理后,钢中未溶相主要有富Nb的M...     

药皮合金元素对FV520(B)钢焊缝组织和韧性的影响

在焊条药皮中添加中碳锰铁和镍粉将Mn、Ni元素过渡到FV520(B)钢焊缝,用金相分析、冲击试验、XRD分析和SEM观测等手段研究了药皮合金元素对FV520(B)钢焊缝的组织和韧性的影响。结果表明:FV520(B)钢焊缝组织以回火索氏体和板条马氏体为主,出现残余奥氏体和二次析出相;随着合金元素的增加,焊缝的组织更加细小致密,马氏体片层更加均匀细小,分布更加弥散。与酸性药皮相比,碱性药皮过渡合金元素的效果更显著,因此焊缝的冲击韧性更优良。用药皮过渡Mn、Ni能提高焊缝中奥氏体的含量,进而改善FV520(B)钢焊缝的冲击韧性。与Mn相比,添加Ni提高焊缝韧性的效果更为显著。     

退火工艺对冷轧中锰中铝低密度钢组织与性能的影响

钢铁材料的轻量化、增强增韧是目前先进金属材料的重点研究方向.在钢材固有合金元素的基础上,通过添加一些增强其性能的元素及低密度元素等,可以显著改善钢材的综合性能,并降低零件质量.随着汽车工业的快速发展,轻量化汽车用钢的研发和应用越来越深入和广泛.目前,Fe-Mn-Al-C系低密度钢主要借鉴了中/高锰钢成分设计、热处理工艺、组织性能调控的研究思路,形成性能优异、成本合理的高强韧性钢.本工作针对中锰中铝低密度钢(12. 4% Mn,4. 7% Al,0. 1% C(均为质量分数,下同))的成分特点,通过对冷轧试样在Ac1与Ac3附近进行退火处理,调控基体相稳定性和组织构成.结果表明:γ奥氏体稳定性与原始组织形态、退火条件和拉伸应力有很大的关联,其组织转变遵从γ奥氏体→ε马氏体→α'马氏体规律;在850 ℃退火、保温15 min条件下,获得了抗拉强度、延伸率分别为854 MPa、44. 3% ,强塑积为37. 8 GPa·%的优异性能.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.