合金元素和控轧控冷工艺在管线钢研制中的应用

通过在管线钢中添加Mn、Nb、V、Ti和Mo等合金元素与采用控轧控冷工艺可获得良好的微观组织和综合力学性能.具体论述了控轧控冷过程中合金元素和控轧控冷工艺参数对管线铜微观组织和力学性能的影响;同时分析了微合金元素(Nb、V、Ti)碳氮化物的析出行为.结果表明,在适当范围内降低终轧温度和终冷温度,提高轧后冷却速度和增大精轧总变形量都可有效改善钢的综合性能.     

含Nb细晶高强IF钢热变形行为的析出热力学

以新型含Nb细晶高强IF钢为研究对象,运用规则溶液亚点阵模型计算了实验钢从均热(1523K)冷却至室温(293K)的各个工艺过程中碳氮化物析出相的平衡体积分数、析出相的组成成分、各组元的平衡质量分数。计算结果表明,从均热到冷却至室温(1523K~293K)的过程中,随着温度的降低,固溶于基体中的Nb、C、N元素的质量分数逐渐减小,析出相平衡体积分数先增大后减小,NbN在析出相中比例逐渐降低,NbC在析出相中比例逐渐增加。至室温(293K)时,Nb和N元素几乎全部析出,碳氮化物不再继续析出。     

Nb微合金钢析出行为的热力学计算

以析出热力学为基础,对Fe-Nb-C-N系统中奥氏体／碳氮化物的热平衡过程,计算了不同温度下碳氮化物析出相的平衡摩尔分数、化学驱动力、各组元的原子分数及奥氏体组分等．结果表明,随着温度的降低,析出相的平衡摩尔分数增大,溶解在奥氏体中的各组元的摩尔分数降低,析出相的化学驱动力增大．在低温条件下,Nb和N元素巳基本析出．碳化物在析出物中所占的比例主要取决于钢的成分和温度．对于同一成分的钢种,这一比值随着温度的降低而增大．     

高级别管线钢板的组织特征与析出强化

利用扫描电镜、透射电镜对炉卷轧机生产的高级别X70,X80管线钢板的显微组织与析出相进行了观察与分析,并对管线钢板组织中碳氮化物析出相的成分、相结构以及粒度分布进行了定量分析,并采用Ashby-Orowan修正模型对析出粒子的强化贡献进行了理论计算.结果表明:X70,X80管线钢板的组织以针状铁素体为主,其高密度位错与交叉分布的大角度晶界特点保证了管线钢的高强韧性;X70,X80管线钢板中的析出相主要有两种类型,一种为尺寸较小的NbC析出相(1～30 nm),另一种为尺寸较大的(Ti,Nb)(C,N)复合析出相(50～300 nm),两种类型均为面心立方结构;生产工艺对析出相的粒度分布有明显影响,避开900～950 ℃碳氮化物的快速析出温度区间,以及适当增加冷却速度可以有效提高20 nm以下的析出粒子体积分数,细化析出物尺寸,从而提高析出强化对屈服强度的贡献.     

Ti和Ti-V微合金化低碳贝氏体钢组织性能及析出行为的研究

利用场发射扫描电子显微镜(FE-SEM)、高分辨透射电子显微镜(HRTEM)和能谱仪(EDS)等,研究了不同Ti含量的低碳贝氏体钢的显微组织和析出相的成分、尺寸、形貌以及分布等特征.结果表明:在450℃和520℃保温2h,三种实验钢组织为粒状贝氏体.与低Ti实验钢相比,高Ti及Ti-V复合实验钢的屈服强度增加了150MPa以上.高Ti钢中纳米级析出相有两种类型:一种大于15nm的TiC析出相;另一种是在10nm以下,具有面心立方结构的(Ti,Mo)C复合析出相.Ti-V钢基体中存在大量尺寸在10nm以下的(Ti,V,Mo)C复合析出相.     

X70针状铁素体管线钢中的析出行为研究

利用透射电镜和X射线能谱研究了Nb-V-Ti微合金X70针状铁素体管线钢中析出物的形貌、结构和化学成分.观测结果表明所研究钢中的析出物可分为两大类:一类为高温析出的尺寸较大的复合析出物,尺寸较大的方形TiN粒子为复合析出物的核心,而含Nb的尺寸较小的析出物附着在其一侧或多个侧面生长.在较低温度下,Nb的碳化物和(或)碳氮化物在位错和亚界面上非均匀形核析出,尺寸较小,外貌呈球形.根据钢的化学成分、热力学和X射线能谱分析认为,NbC粒子是本工艺条件下所研究的Nb-V-Ti微合金X70针状铁素体管线钢中的主要析出相.     

低活化铁素体/马氏体耐热钢中MX型碳氮化物强化研究进展

低活化铁素体/马氏体耐热(RAFM)钢在强辐照条件下仍具有良好的力学性能、导热性及抗热膨胀性,被认为是目前核聚变反应堆的首选结构材料,但是其较低的高温蠕变抗力和抗辐照性能极大限制了其使用温度,进而影响了核聚变反应堆的转换效率。纳米级MX型碳氮化物作为钢中重要的强化相,在高温下仍具有良好的稳定性,能够有效阻碍位错的运动及湮灭,可以有效提高钢的高温蠕变性能。此外,纳米级MX型碳氮化物的析出还可以增加钢中的界面比,而界面是良好的缺陷陷阱,可以有效诱捕辐照产生的离位原子、空位等点缺陷,从而提高钢的抗辐照性能,因此进一步增加钢中的MX型碳氮化物含量被认为是提升RAFM钢力学性能的有效途径。目前,提高RAFM钢中MX型碳氮化物强化最有效的方式主要有三种:氮化物强化工艺、形变热处理工艺(TMT)和Ti元素的添加工艺。三种工艺均能有效提高钢的高温拉伸及蠕变性能,但它们对钢综合力学性能的影响并不完全相同。氮化物强化工艺主要是通过降低钢中的C含量同时提高N含量,从而达到促进MX型碳氮化物析出的目的。但由于钢中的N含量较高,极易形成粗大的TaN夹杂,在低温条件下,钢的临界裂纹尺寸会大幅降低,TaN夹杂就会成为冲击过程的裂纹源,从而使钢的韧脆转变温度(DBTT)大幅升高。TMT工艺主要是将钢加热到奥氏体化温度以上进行保温,使钢中碳化物充分溶解,之后降温至M_(23)C_6型碳化物熔点以上,对钢引入较大的变形量,从而产生大量位错,促进MX型碳氮化物的形核。由于较高的固溶温度和较大的变形量,TMT处理后,钢具有较大的晶粒尺寸和较高的应力状态,从而使钢的冲击性能大幅降低。Ti元素添加工艺主要是在钢中引入Ti元素,Ti是良好的碳氮化物形成元素,在钢中极易与C、N元素结合形成MX型碳氮化物,从而提高钢中的MX型碳氮化物含量。与氮化物强化及TMT工艺不同,Ti元素添加后,钢中并未出现粗大的夹杂物及过大尺寸的晶粒,其表现出最佳的综合力学性能,与传统RAFM钢相比,其高温力学性能及室温冲击性能均大幅增加,仅DBTT值略有升高。本文从强化机理出发,重点介绍了近年来MX型碳氮化物强化RAFM钢的发展情况,并分析对比了三种MX型碳氮化物强化工艺对钢综合力学性能的影响。此外本文还指出了RAFM钢未来发展过程中可能遇到的其他问题,并对今后的研发重点进行了简要的分析。     

Nb、Ti微合金钢中碳氮化物固溶与再析出的研究

利用光学显微镜(OM)、透射电子显微镜(TEM)研究了再加热温度、奥氏体区变形温度和组织转变温度的变化对Nb、Ti微合金钢组织性能及其碳氮化物固溶与再析出行为的影响.结果表明:钢中加入铌,主要利用铌的碳氮化物在奥氏体形变过程中的再析出,抑制形变奥氏体的再结晶,在随后的组织演变过程中细化了组织;而钢中加入较高含量的钛,主要利用钛的碳化物在铁素体中的析出,产生明显的沉淀强化作用.这主要是铌、钛的碳氮化物固溶后,在奥氏体和铁素体中再析出的不同所造成的.钢中复合加入Nb-Ti后既起到细化晶粒的作用,又起到析出强化的作用.细晶强化既提高钢的强度又提高钢的韧性,但沉淀强化在大幅提高钢的强度的同时恶化了钢的韧性.     

Nb、Ti微合金钢中碳氮化物固溶与再析出的研究

利用光学显微镜(OM)、透射电子显微镜(TEM)研究了再加热温度、奥氏体区变形温度和组织转变温度的变化对Nb、Ti微合金钢组织性能及其碳氮化物固溶与再析出行为的影响。结果表明:钢中加入铌,主要利用铌的碳氮化物在奥氏体形变过程中的再析出,抑制形变奥氏体的再结晶,在随后的组织演变过程中细化了组织;而钢中加入较高含量的钛,主要利用钛的碳化物在铁素体中的析出,产生明显的沉淀强化作用。这主要是铌、钛的碳氮化物固溶后,在奥氏体和铁素体中再析出的不同所造成的。钢中复合加入Nb-Ti后既起到细化晶粒的作用,又起到析出强化的作用。细晶强化既提高钢的强度又提高钢的韧性,但沉淀强化在大幅提高钢的强度的同时恶化了钢的韧性。     

预应变对Nb微合金化09MnNiDR低温钢高温塑性的影响

利用光学和电子显微镜观察断口组织,并测定断面收缩率来研究预拉伸应变对Nb微合金化低温钢09MnNiDR高温塑性的影响。当试样进行5%变形量预拉伸,800℃时断口组织主要为铁素体,晶界处有网状先共析晶界铁素体,断面收缩率为63%;900℃时断口组织主要为贝氏体和针状铁素体以及大量碳氮化物,断面收缩率降至35%;1000℃时断口组织主要为板条马氏体,断面收缩率升至95%。与未进行预应变试样相比,在800～920℃的温度区间,断面收缩率显著降低,预应变明显恶化了Nb微合金化09MnNiDR钢的高温塑性,这主要与预应变促进了尺寸为十几纳米至几十纳米Nb碳氮化物的沿晶界析出有关。     

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.     

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.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.