不同制备工艺对锻造高速钢轧辊组织和性能的影响

采用光学显微镜、扫描电镜、X射线衍射仪、洛氏硬度计和磨损试验机对比研究了电渣重熔、喷射成形以及粉末冶金工艺生产的锻造高速钢轧辊的组织性能。结果表明,采用电渣重熔工艺所得锻造高速钢轧辊组织中存在明显沿锻造方向分布的网状共晶碳化物,碳化物尺寸粗大,分布不均,导致其耐磨性最差;喷射成形工艺所得锻造高速钢轧辊网状碳化物组织得到明显改善,但局部区域碳化物偏聚较严重,碳化物尺寸较大且主要以M₆C型为主,其耐磨性比电渣重熔工艺有明显提升;粉末冶金工艺所得锻造高速钢轧辊组织晶粒细小,碳化物细小且弥散均匀分布,碳化物类型中MC型占比很高,表现出最优的耐磨性能。根据3种制备工艺下的组织和性能分析,并结合目前3种制备工艺的成熟度、经济性和制造能力,未来可对喷射成形工艺做进一步研究,并逐步在较大规格锻造高速钢轧辊中推广应用。     

改进电渣工艺对大截面M2高速钢的影响

选取?100 mm(常规工艺生产)和?120 mm(电渣工艺改进)的大截面M2高速钢为研究对象,比较2种规格的M2高速钢不同部位的碳化物和硬度、抗弯强度,分析改进电渣工艺对大截面M2高速钢中碳化物和性能的影响。结果表明:2种规格的大截面M2高速钢淬-回火态的硬度在不同部位的差异均较小,但与常规工艺生产的?100 mm大截面M2高速钢相比,电渣工艺改进后的?120 mm的M2高速钢组织均匀性好,碳化物条带宽度降低、网状特征减弱,各部位的抗弯强度差别较小。     

冷却速度对高速钢M2C共晶碳化物的影响

采用砂型和金属型铸造制备M2高速钢铸锭,研究了冷却速度变化对高速钢M2C共晶碳化物形态及性质的影响,探讨了M2C共晶碳化物形态变化的机理。结果表明,冷却速度增加,莱氏体网细化,铸态偏析得到改善;M2C形态由片层状转变为棒状,碳化物中合金元素含量降低,高温分解产生的MC碳化物和M6C＋MC复合碳化物数量减少。共晶反应时,共晶碳化物和奥氏体相之间的生长速度差异决定了M2C共晶碳化物的形态。     

高速钢坯料制备工艺的问题与对策

现行的高速钢坯料制备工艺主要是电渣重熔和粉末冶金两大类。其中电渣重熔锭比普通冶炼模铸钢锭的组织致密,明显改善了初始共晶碳化物的分布,但是电耗过高,生产中产生的氟化物对环境的污染严重;粉末冶金虽然从根本上解决了碳化物偏析和粗大的问题,但其工艺复杂,成本过高,应用受到限制。而半固态连铸工艺既解决了初始碳化物偏析和粗大问题,又克服了电渣重熔中电耗高、环境污染以及粉末冶金成本高的缺点,是值得重视的一个新工艺。     

高速钢坯料制备工艺的问题与对策

现行的高速钢坯料制备工艺主要是电渣重熔和粉末冶金两大类。其中电渣重熔锭比普通冶炼模铸钢锭的组织致密，明显改善了初始共晶碳化物的分布，但是电耗过高，生产中产生的氟化物对环境的污染严重，粉末冶金虽然从根本上解决了碳化物偏析和粗大的问题，但其工艺复杂，成本过高，应用受到限制。而半固态连铸工艺既粉末冶金成本高的缺点，解决了初始碳化物偏析和粗大问题，又克服了电渣重熔中电耗高、环境污染以及是值得重视的一个新工艺。     

电渣重熔金属熔池深度的实用测定方法

介绍一种实用的电渣重熔熔池深度的测定方法,通过测定可绘制熔池形状图,并介绍了据此改善工艺参数,提高电渣锭质量的实例。     

M2高速钢工业铸带中共晶碳化物及其演化

在工业机组上制备了M2高速钢铸带,采用扫描电镜和透射电镜研究了热处理和热轧对铸带中的共晶碳化物特征的影响.结果表明:双辊薄带连铸工艺可以获得共晶碳化物尺寸细小、分布均匀的高速钢铸带,铸带中存在较多的M2C亚稳相碳化物;热处理后M2C碳化物分解生成M6C和MC碳化物,碳化物得到进一步细化;由M2工业铸带直接热轧而成的薄带中仍存在一些呈断续网状分布的碳化物,先进行合适的热处理再进行热轧对M2工业铸带更为合适.     

一种新型变质剂对高速钢组织与力学性能的影响

采用电渣重熔工艺制备高速钢材料,借助光学显微镜和摆锤冲击试验机研究变质剂对高速钢轧辊材料微观组织和冲击性能的影响。结果表明：制备过程中加入变质剂能改变高速钢中共晶碳化物的形貌,部分鱼网状的共晶碳化物组织发生断裂,颗粒状碳化物增多,基体中晶粒更加细小;经过热处理这种趋势变得更加明显,因此高速钢的冲击韧性得到提高,其冲击韧性由8.7 J/cm2增加到9.8 J/cm2。     

电渣重熔GCr15轴承钢铸锭和退火材中大块碳化物的晶体类型及其溶解规律

我们研究电渣重熔GCr15轴承钢中大块碳化物,是为了提高轴承的使用寿命。关于GCr15轴承钢中大块碳化物的晶体类型,过去存在两种看法:一种认为是合金渗碳体;另一种认为是(Fe,Cr)_7C_3型碳化物.我们的研究工作试图回答以下四个问题:1.确定GCr15轴承钢铸锭中大块碳化物的晶体类型;2.确定退火材中较大碳化物的晶体类型;3.铸锭中大块碳化物的溶解温度;4.退火材中较大碳化物的溶解规律。试验样品取自大冶钢厂电渣重熔轴承钢,铸态试样从解剖的两支1.2吨锭头部截取,一支经扩散退火,一支未经扩散退火。退火材试样是经扩散退火后,从轧成直径38毫米钢棒上取下。钢样的化学成分和热处理制度见表1。     

M2高速钢共晶碳化物形态与稳定性研究

采用不同尺寸模具浇注了M2高速钢,研究了冷却速度变化对其铸态组织特别是共晶碳化物形态、结构的影响规律.结果 表明,当铸锭直径尺寸减小时,冷却速度加快,高速钢碳化物分布更均匀,M2C碳化物形态由片状变成纤维状.与片状碳化物相比,纤维状碳化物稳定性更低,加热时更容易分解,使碳化物明显球化、尺寸显著减小,提高了高速钢组织均匀...     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

The Mirror with Patterns of Auspicious Animals and Grapes——Exquisite cast mirror and the technology of surface tin-enrichment by rubbing-in and infiltration of tin-rich powder

<正>Bronze mirrors were used by the Chinese people before the introduction of the glass mirror.Only after it was replaced by the glass mirror did the bronze mirror gradually retreat from people's lives.Different styles of bronze mirrors were made in different historical periods,particularly in the Warring States Period,the Han and Tang Dynasties,which were the three peaks of the development of bronze mirror arts in ancient China.The casting techniques were exquisite.The surface of the bronze mirror was smooth and bright enough to reflect one's image,and there were scarcely any casting defects on the mirror surface.On the back of the bronze mirror,there were rich depictions of Arts and Humanities,and the ornamentations were also     

The 9th China International Diecasting Congress & Exhibition

The 9th China International Diecasting Congress ＆ Exhibition was held on July 22-24, 2014 at Shanghai New International Expc Centre. This exhibition was the most successful over the years, with over 6890 visitors and 155 exhibitors, and the exhibition area increased by 30% from 9,500 square meters in 2012 to 12340 square meters. Die casting enterprises from a total of 24 countries and regions, including China mainland, Chinese Taiwan and Hong Kong, South Korea, Japan, Germany, India, Thailand, Malaysia, the United States, Russia, Australia, Iran, Ukraine, Brazil, Colombia, Singapore, Austria, Canada, Croatia, France, Turkey, United Kingdom, Vietnam, attended the congress and exhibition.     

Introduction of the Fluid Control Engineering Institute of Kunming University of Science and Technology

正The Fluid Control Engineering Institute of Kunming University of Science and Technology was set up in 1996.The researches of institute concentrate on electro-hydraulic(pneumatic)servo/proportional control and hydromechatronics.The Institute is committed to research and development of electro-hydraulic control of high-end technical equipment in ferrous metallurgy refining produc-     

RARE METALS Volume Contents

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Antimony Induced Crystallization of Amorphous Silicon

Antimony induced crystallization of PVD (physics vapor deposition) amorphous silicon can be observed on sapphire substrates. Very large crystalline regions up to several tens of micrometers can be formed. The Si diffraction patterns of the area of crystallization can be observed with TEM (transmission electron microscopy). Only a few and much smaller crystals of the order of 1μm were formed when the antimony layer was deposited by MBE (molecular beam epitaxy) compared with a layer formed by thermal evaporation. The use of high vacuum is essential in order to observe any Sb induced crystallization at all. In addition it is necessary to take measures to limit the evaporation of the antimony.     

A CUMULATIVE FATIGUE DAMAGE RULE UNDER THE ALTERNATIVE OF CORROSION OR CYCLIC LOADING

Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic loading was proposed. The specimens of aluminum alloy LY12-CZ soaked in corrosive liquid for different times were tested under the constant amplitude cyclic loading to obtain S-N curves. The test was carried out to verify the proposed cumulative fatigue damage rule under the different combinations among corrosion time, loading level, and the cycle numbers. It was shown that the predicted residual fatigue lives showed a good agreement with the experimental results and the proposed rule was simple and can be easily adopted.