关于WC-Co硬质合金的强度和结构问题(Ⅳ)

综述了WC-Co硬质合金强度和结构方面的研究结果,阐明WC-Co硬质合金具有颗粒型复合强化材料的本质特征.据此,对WC-Co硬质合金微观结构及其制造工艺技术的一些问题进行了探讨.     

硬质合金横向断裂强度不确定度评定

硬质合金横向断裂强度是反应硬质合金质量的主要指标之一。通过剖析硬质合金横向断裂强度试验方法,对测试结果的测量不确定度进行分析评定,从而确定了影响硬质合金横向断裂强度测定结果的主要因素,提高硬质合金检测水平。     

关于WC-Co硬质合金的强度和结构问题(Ⅲ)

综述了WC-Co硬质合金强度和结构方面的研究结果，阐明WC-Co硬质合金具有颗粒型复合强化材料的本质特征。据此，对WC-Co硬质合金微观结构及其制造工艺技术的一些问题进行了探讨。     

关于WC-Co硬质合金的强度和结构问题(Ⅱ)

综述了WC-Co硬质合金强度和结构方面的研究结果，阐明WC-Co硬质合金具有颗粒型复合强化材料的本质特征。据此，对WC-Co硬质合金微观结构及其制造工艺技术的一些问题进行了探讨。     

关于WC—Co硬质合金的强度和结构问题（Ⅳ）

综述了WC—Co硬质合金强度和结构方面的研究结果，阐明WC-Co硬质合金具有颗粒型复合强化材料的本质特征。据此，对WC-Co硬质合金微观结构及其制造工艺技术的一些问题进行了探讨。     

球磨参数对TiC基钢结硬质合金性能的影响

本实验研究了球磨方式和球磨时间对于钢结硬质合金致密化的影响 ,结果发现 :在一定的球磨时间里 ,行星式高能球磨相对于普通球磨方式而言 ,可以减少粉末在球磨过程中的氧化程度 ,促进钢结硬质合金在烧结过程中的致密化进程 ,提高材料的密度和强度。     

提高硬质合金顶锤质量问题的探讨

硬质合金顶锤质量(使用寿命)的研究不单是提高顶锤质量的问题,而且对整个硬质合金质量水平的提高具有普遍意义。本文重点研究论述WC—8％Co顶锤(六面顶)的质量问题。通过顶锤解剖和实验结果进行综合分析,得出了在合金是两相结构的前提下,决定顶锤质量的主要因素是:合金组织结构中的WC相晶粒度及其分布,孔隙度及孔的大小的综合影响结果。本文研究确定了生产顶锤所需的原料,技术条件和一系列参数,并确定了WC—8％Co顶锤合金各项检查指标的控制参数。     

关于WC-Co硬质合金的强度和结构问题(Ⅰ)

综述了WC—Co硬质合金强度和结构方面的研究结果，阐明WC—Co硬质合金具有颗粒型复合强化材料的本质特征。据此，对WC—Co硬质合金微观结构及其制造工艺技术的一些问题进行了探讨。     

WC-Co-Ni硬质合金与45号钢焊条电弧焊研究

为研究硬质合金与碳钢焊条电弧焊连接的可行性,选取低碳钢焊条J422、铸铁焊条Z308和Z408对WC-10Co-20Ni硬质合金与45号钢进行焊条电弧焊连接,通过微观组织分析、X射线衍射(XRD)物相分析、硬度分布测试及弯曲强度测试等手段,对比分析了3种焊条所焊接头的组织与性能,研究结果表明:采用J422焊条焊接后,焊缝组织以马氏体和共晶碳化物为主,并含有η碳化物层,接头结合强度弱,不适于焊接硬质合金;Z308和Z408焊条可以抑制界面η碳化物层的生成,但在焊缝中有大量夹渣,影响接头性能;Z408焊条焊缝有少量的共晶碳化物产生,但因熔敷金属的膨胀系数介于硬质合金与钢之间,能有效缓解焊接应力,较适合用于硬质合金的焊接。使用Z408焊条焊接时,采取适当提高电流,增加摆动频率等工艺措施,可以减少夹渣的数量和分布状态,促进成分和组织均匀化,有利于提高接头性能,弯曲强度可以达到WC-10Co-20Ni硬质合金母材强度的90%以上。     

梯度硬质合金的研制

采用正碳烧结工艺研制梯度硬质合金，合理选择配方中的缺碳量以及正碳烧结工艺参数时，可生产出表面硬度高、耐磨性好，内部强度高、韧性好的梯度硬质合金。实验中，钴含量相同的梯度硬质合金比钴相均匀硬质合金的抗弯强度和耐磨性分别提高了５．５％和２５．６％。     

Mechanical properties of fine grained hardmetals produced by pressureless and pressure assisted sintering technologies

Pressureless sintering and the two pressure assisted sintering technologies – sintering + hot isostatic pressing (sinter-HIP) and field assisted sintering technology (FAST) were used to produce a fine grained WC-6 Co hardmetal.

In order to compare the mechanical properties of the hardmetals, which result from different sintering technologies, the material strength was determined. In the present study the uniaxial three point bending test and the biaxial ball on three balls test were used as strength measuring methods. The results were described by the Weibull distribution function.

Additionally, the paper will analytically compare the two tests by describing the relation of the strength of the samples to their effective volumes. Based on this procedure components having arbitrary shapes and volumes can be designed.     

New Grades of Hardmetals for a Rock Cutting Tools

A concept is developed for creating hardmetals for rock cutting tools. The concept pays particular attention to increasing energy absorption and the fatigue strength of hardmetals. In order to provide high rock cutting tool efficiency it should be fitted with hardmetal inserts which exhibit high bending strength, fracture toughness, total work of deformation, and energy absorption coefficient. This has been realized in the development of new grades of hardmetals for rock cutting tools. The efficiency of rock cutting tools fitted with inserts made from the new grades of hardmetal exceeds that of similar tools fitted with standard hardmetals inserts by a factor of 2.8     

Electrical Conductivity and Strength Changes in Green Compacts of Iron Powder When Heated in Range 50–400°C in Air

Abstract

Based on considerable technological development and comprehensive work in process engineering, a method has been developed for short-time induction sintering of hardmetals which combines increased production throughput with savings in treatment time and improvement of the final product. The process is applicable to conventional WC–Co and WC–TiC–Co hardmetals and can be readily transferred to other cemented carbide systems. PM/0217     

硬质合金激光表面强化的试验与应用

介绍了运用激光表面强化技术对硬质合金材料制品进行强化处理的试验研究。并通过实际应用，证实了激光表面强化处理具有使硬质合金制品的抗弯强度、耐磨性能大为提高的显著效果。     

Monte–Carlo Based Method for Predicting Extreme Value Statistics of Uncertain Structures

In the present paper, a simple method is proposed for predicting the extreme response of uncertain structures subjected to stochastic excitation. Many of the currently used approaches to extreme response predictions are based on the asymptotic generalized extreme value distribution, whose parameters are estimated from the observed data. However, in most practical situations, it is not easy to ascertain whether the given response time series contain data above a high level that are truly asymptotic, and hence the obtained parameter values by the adopted estimation methods, which points to the appropriate extreme value distribution, may become inconsequential. In this paper, the extreme value statistics are predicted taking advantage of the regularity of the tail region of the mean upcrossing rate function. This method is instrumental in handling combined uncertainties associated with nonergodic processes (system uncertainties) as well as ergodic ones (stochastic loading). For the specific applications considered, it can be assumed that the considered time series has an extreme value distribution that has the Gumbel distribution as its asymptotic limit. The present method is numerically illustrated through applications to a beam with spatially varying random properties and wind turbines subjected to stochastic loading.     

Abrasion and toughness property maps for WC/Co hardmetals

Abstract

WC/Co hardmetals are generally designed for applications where resistance to wear, particularly abrasion or erosion, needs to be high but without the low toughness often found in very hard materials. Consequently, mapping the relation between wear characteristics and toughness is fundamental to the process of grade selection in commercial hardmetals. In current research at NPL wear resistance has been assessed using the ASTM B611 abrasion test method and toughness through Palmqvist fracture toughness. Both these tests are now well understood, especially the uncertainties associated with the measurements. Both of the two main types of property map are considered: those concerned with properties associated with end use, e.g. abrasion and toughness; and those concerned with relating microstructural parameters to the property of interest i.e. abrasion and its dependence on WC grain size. Comments are made on the effects of WC grain size distribution and mean grain size.     

Utilisation of nickel plant leach residue by sintering technique

This paper presents useful data on process parameters and experimental conditions for producing quality sinter based on laboratory scale experiments for sintering of a completely waste material, i.e., nickel plant leached residue for its effective utilization to extract nickel and chromium in the alloyed form by producing chromium based pig iron. Some attempts have also been made to evaluate the results obtained from several laboratory scale experiments for estimation of strength and productivity. It has been found that, by implementation of the process waste released from a nickel plant (based on reduction-roast-ammonia leaching) can be used to produce value added products thereby adding to the overall economics of the nickel production technology.     

Negative regulation of the anti-human immunodeficiency virus and chemotactic activity of human stromal cell-derived factor 1alpha by CD26/dipeptidyl peptidase IV

A method to characterize the energy distribution in the whole photon field is valuable when designing an accelerator for choosing target and flattening filter or scan pattern. Another field of application is beam characterization for treatment planning systems or other dosimetric purposes. This work is focused on the energy distribution in different 50 MV bremsstrahlung beams with different scanning of electrons on three different targets. Fluence differential in energy and angle at the exit of each target has been determined by Monte Carlo calculations for a narrow beam. Data for broad beams were obtained by convolution of the narrow beams with different scan patterns. Photon energy fluence differential in energy at SSD 100 were thus found to be rather different for the targets studied. The results are presented as mean energy profiles and narrow beam half-value layer (HVL) in water. Two different experimental setups were used to measure HVL at the central axis and at off-axis positions. The two methods gave results which differ by 5%-6% and the calculated data where within these experimental results. In conclusion, the presented method for characterization of the photon field energy distribution is well within the experimental results and can thus be used to improve accelerator design or dosimetric calculations, e.g., for treatment planning.     

关于三维网状高孔率材料抗拉强度公式中指数项的讨论

以典型的三维网状高孔率金属—泡沫镍为实验材料 ,进行系列的抗拉强度测试。通过所得实验数据对有关公式的应用验证 ,分析讨论了这些公式中指数项的取值问题。对于泡沫镍这类具有中等塑性的高孔率材料而言 ,该指数项取 1.2 5比取 1.5 (即 3/ 2 )显得更为合适或合理。     

Span-Dependent Distributions of the Bending Strength of Spruce Timber

Tests data of bending strengths of a large number of timber beams of different spans obtained at the Swedish Institute for Wood Technology Research reveal a statistical structure that can be represented in a simple probabilistic model of series system type. A particular feature of the data from one of the large test series is that unintentionally the data became randomly censored upwards. This censoring of the data rules out both the moment estimation method and the maximum likelihood method. Instead valid parameter estimates can be obtained by maximizing the posterior density defined as the likelihood function multiplied by a suitably chosen noninformative prior density (MP method). Subsequently using bias factors assessed by simulation ensures that the corrected MP estimates are unbiased. A closed form analytical expression for the distribution function of the bending strength of a beam with any given number of defect clusters follows from the obtained distribution model for the bending strength of the random single defect cluster. The empirical distribution function of bending test results for a sample of beams with two defect clusters is well predicted, and for long beams with several defect clusters the same is the case in the lower tail up to at least about the 50% probability level.