凹槽形补焊缝维氏硬度的梯度试验

在铸钢件补焊工艺评定时,要求对试样中的焊缝、热影响区、母材部位进行维氏硬度的梯度试验。硬度压痕与压痕之间必须呈等间距,且为直线行排列。选用了HV-120型维氏硬度计进行试验,用两块方形磁铁起到固定试样的作用;同时,还要用游标卡尺的精度来保证压痕之间的距离准确。其操作方法简单易行,达到了试样成直线平稳移动的效果,使压痕的间距尺寸误差为±0．02mm。定位准确,硬度压痕的对角线清晰,数值可靠,符合规程的要求。     

DP780高强钢电阻焊接头维氏硬度测量不确定度评定

采用430SVD型数显显微硬度计,通过直接评定法对DP780高强钢电阻焊接头的母材、热影响区及焊缝区分别进行了维氏硬度试验,分析了不同因素对测量结果产生的影响,并对维氏硬度测量结果进行了不确定度评定。结果表明:该DP780高强钢电阻焊接头母材、热影响区及焊缝区维氏硬度的测量不确定度分别为9,9,10 HV,均满足GB/T 4340.2—2012中表5要求的硬度计最大允许误差,该维氏硬度检测方法、检验水平能够满足国家标准的要求。与硬度计本身硬件设施误差相比,压痕对角线长度的测量对合成不确定度评定结果的影响更大。     

FV520B钢和Q235A钢焊接接头的维氏硬度试验

在没有x-y轴移动装置的HV-120型维氏硬度计上,仅增加简单的辅助工具,成功完成了FV520B马氏体沉淀硬化不锈钢和Q235A钢V型焊缝焊接接头的维氏硬度试验。结果表明:FV520B钢焊接接头的焊缝、熔合线、热影响区以及母材的维氏硬度差别较小,硬度分布比较均匀,焊接质量满意;Q235A钢焊接接头的焊缝、熔合线、热影响区以及母材的维氏硬度差别更小,硬度分布更加均匀,焊接质量更好。该试验方法操作简单、方便实用,可以完成V型焊缝焊接接头的维氏硬度测试,对使用没有x-y轴移动装置的维氏硬度计的企业进行焊缝质量评定具有借鉴作用。     

咨询与服务

《理化检验》物理编辑部: 编辑同志,您们好!通常我们把布氏、洛氏、维氏等多用途的硬度计称为万能硬度计(universal hardness tester),最近从外文杂志上见到有关万能硬度(Universal hardness)的说法,用Hu表示,所用的压头也是两相对面间夹角为136°的正四棱锥金刚石压头,但不是测量压痕对角线,而是测量压痕深度,计算公式如下:Hu=F/(26.43h~2) Hu的单位为N/mm~2,以区别于维氏硬度HV(所用的单位为kgf/mm~2),不知我们国内是否有万能硬度这种说法,望予赐教。     

金属材料维氏硬度试验测量不确定度的评定

金属材料维氏硬度试验的测量不确定度主要来源于试验力、标准硬度块、压痕对角线长度的测量以及硬度计本身、试验结果的数值修约等。根据GB/T 4340.1-2009对硬度计和标准硬度块的要求,结合生产实际,计算了不同试验力下维氏硬度试验的测量不确定度。结果表明:硬度计的最大允许误差引起的测量不确定度所占的权重最大;对于同一维氏硬度,试验力越大,维氏硬度试验的测量不确定度则越小,因此在日常检测中,在满足要求的情况下,应尽可能选择较大的试验力,减小测量不确定度,使试验结果更加准确可靠。     

对焊接接头热影响区维氏硬度试验的探讨

分析了焊接热循环对焊接接头热影响区组织和维氏硬度分布的影响。结果表明，热影响区维氏硬度峰值出现在距熔合线约0.5mm以内的过热区内，热影响区维氏硬度分布梯度很大，使试验压痕位置成为产生试验误差的主要原因。因此，建议在制订标准时，应用确规定焊接接头热影响区维氏硬度试验的压痕位置，第一点压痕位置应在距熔合线约0.5mm以内的过热区内，每一压痕线上每一区域至少3个压痕，间距为0.5-1mm。     

硬度计载荷误差的分析与调整

对于最广泛应用于生产和科学研究的洛氏、布氏、维氏等各种工作用硬度计,其工作原理均是采用一个压头,在一定的载荷作用下压入试件、以压入深度或压痕面积上所承受的载荷来表示硬度值。从这个工作原理可以知道,压头的物理性能和几何精度、测量压痕用的装量的精度及载荷的精度是硬度计示值准确性的三大因素。载荷是硬度计准确性     

基于Labview的显微维氏硬度压痕测量系统的开发

本文在显微维氏硬度计的基础上通过Labview软件设计维氏硬度测量系统,实现对压痕对角线长度的测量,进而可以直接求得维氏硬度值。其中压痕采用三种测量方法获取对角线长度,通过三种方法的比较分析寻求最优测量法。该测量系统实现了硬件结构与软件平台的完美对接,硬度计通过设计改良,确保压头在与试样接触时试样处于水平状态,有效避免压痕结果出现误差。Labview软件平台界面清晰明了,操作过程简洁,具备进一步开发的潜能。     

布氏硬度值与维氏硬度值之间的关系

大家知道,维氏硬度试验法中之所以规定采用正四棱锥体,两相对面夹角为136°的金刚石压头,主要是为了使维氏硬度值尽量接近布氏硬度值。用维氏压头以任何载荷压人试件表面其压人角~*均为44°,即保持几何相似。因此,在这种情况下.不同材料的维氏硬度值可相互比较,同种材料的维氏硬度值相同。依 GB 231—63《金属布氏硬度试验法》规定,“试验后压痕直径的大小应在0.25D相似文献   

中华人民共和国国家标准 金属维氏硬度试验 第1部分:试验方法

1　范围本标准规定了金属维氏硬度试验的原理、符号及说明、硬度计、试样、试验方法及试验报告。本标准按三个试验力范围规定了测定金属维氏硬度的方法 (见表 1)。表 1试验力范围 /Ｎ硬度符号试验名称Ｆ≥ 4 9.0 3≥ＨＶ5维氏硬度试验1.96 1≤Ｆ <4 9.0 3ＨＶ0 .2～<ＨＶ5 小负荷维氏硬度试验0 .0 980 7≤Ｆ <1.96 1ＨＶ0 .0 1～<ＨＶ0 .2 显微维氏硬度试验本标准规定维氏硬度压痕对角线的长度范围为0 .0 2 0～ 1.4 0 0ｍｍ。特殊材料或产品的维氏硬度试验应在相关标准中规定。2　引用标准下列标准所包含的条文 ,通过在本标准中引用而构成为…     

空间滑动电接触Au镀层硬度测试方法研究

为了获取一种准确有效的Au镀层显微硬度测试方法以满足航天领域的应用需求,本文采用显微维氏硬度法及纳米压痕硬度法研究了Au镀层在不同测试方法及不同测试载荷下的显微硬度值及其标准方差,并依据相关检测技术标准的要求,就检测方法的可行性进行了分析。结果表明:本文优选的Au镀层显微维氏硬度检测参数及测试数据的判定范围满足标准QJ482,同时还能满足压痕深度小于镀层厚度的1/7,避免了基体对测试结果的影响,测试方法可行,测试数据有效。     

国内外金属材料焊缝维氏硬度试验的标准化现状

介绍了国内外金属材料焊缝维氏硬度试验标准体系的最新进展,对比分析了我国现行金属材料焊缝维氏硬度试验标准体系中存在的不足.与国际标准相比,我国现行部分金属材料焊缝维氏硬度试验标准标龄较长,需加快修订.此外,要加强标准间相互引用,实现标准之间的方法统一.     

Analysis of data from various indentation techniques for thin films intrinsic hardness modelling

Due to the influence of the substrate, direct measurement of the hardness of thin films by standard micro-indentation tests is not always possible. In such situation, determination of the intrinsic film hardness requires the analysis of a set of experimental apparent hardness values obtained for different indentation loads. A number of mathematical equations based on various assumptions were proposed in literature for that purpose.Most of the models were established on the basis of standard Vickers indentation. Using these models to process the data obtained by Knoop indentation does not provide the same intrinsic hardness value, even after Knoop/Vickers standard conversion, than the one obtained from Vickers indentation. The same problem arises when processing the data coming from depth-sensing indentation. A method to obtain comparable hardness values is proposed in the present work by considering an “equivalent” Vickers hardness in the case of Knoop indentations and the corresponding Martens hardness for depth-sensing indentation. This method has been used to determine the intrinsic hardness of titanium nitride film.     

316L/S32101异种金属焊接接头的显微组织与力学性能研究

目的 研究乏燃料水池用钢板316L与覆板S32101双相不锈钢的焊接性、接头不同区域显微组织特征及接头与母材之间的性能差异.方法 利用氩弧焊接技术对5 mm厚的316L底板与3 mm厚的S32101覆板以搭接的形式进行焊接,利用金相显微镜、扫描电镜、维氏显微硬度仪和电子万能材料试验机对焊接接头的宏观形貌、显微组织以及力学性能进行研究.结果 316L/S32101焊缝组织主要由铁素体基体、晶界树枝状奥氏体以及晶内细小片状奥氏体所组成;316L侧靠近焊缝处存在一个较窄的熔合区,其组织由奥氏体基体和少许细小分散的铁素体组成,而S32101侧靠近焊缝处组织则由粗大铁素体晶粒和沿晶粒边界分布的若干小块状奥氏体组成.从316L母材区到焊缝区,硬度显著增大,而从焊缝区到S32101母材区,硬度变化很小;焊接接头的抗拉强度高达510 MPa,为两侧316L和S32101母材强度的87.9％和88.6％.结论 在焊接电流为240 A和焊接速度为300 mm/min的条件下,可以通过氩弧焊获得成形良好的搭接接头,且接头的力学性能优异.     

Indentation technique for evaluation of hot hardness and creep of SS 316 end-plug welds of nuclear,fuel pins

The high-temperature mechanical properties of SS 316 end-plug welds of nuclear fuel pins were studied using a hot hardness tester. The hardness was measured as a function of temperature on the base metal, weld pool and heat-affected zone from ambient temperature to 1273 K. Hardness was also measured as a function of dwell time from 873 to 1173 K to evaluate the activation energy for creep. The activation energy of the weld pool was found to be higher than that of the base metal. The indentation technique is very suitable for the evaluation of creep properties of very small components.     

Instrumented and Vickers Indentation for the Characterization of Stiffness,Hardness and Toughness of Zirconia Toughened Al_2O_3 and SiC Armor

Instrumented and Vickers indentation testing and microstructure analysis were used to investigate zirconia toughened alumina(ZTA) and silicon carbide(SiC).Several equations were studied to relate the Vickers indentation hardness,Young's modulus and crack behavior to the fracture toughness.The fracture in SiC is unstable and occurs primarily by cleavage leading to a relatively low toughness of 3 MPa m~(1/2),which may be inappropriate for multi-hit capability.ZTA absorbs energy by plastic deformation,pore collapse,crack deviation and crack bridging and exhibits time dependent creep.With a relatively high toughness around 6.6 MPa m~(1/2),ZTA is promising for multi-hit capability.The higher accuracy of mediar equations in calculating the indentation fracture toughness and the relatively high c/a ratios above 2.5suggest median type cracking for both SiC and ZTA.The Young's modulus of both ceramics was most accurately measured at lower indentation loads of about 0.5 kgf,while more accurate hardness and fracture toughness values were obtained at intermediate and at higher indentation loads beyond 5 kgf respectively.A strong indentation size effect(ISE) was observed in both materials.The load independent hardness of SiC is 2563 HV,putting it far above the standard armor hardness requirement of 1500 HV that is barely met by ZTA.     

Boron-assisted transformation to rod-like graphitic carbons from multi-walled carbon nanotubes in boron-mixed multi-walled carbon nanotube solids

We produced boron-mixed multi-walled carbon nanotube solids (B-mixed MWCNT solids) by heating and pressing the powder of purified MWCNTs mixed with 1, 5, and 10 wt % boron in the temperature range 1400-1800 °C every 200 °C under a constant pressure of 20 MPa in vacuo, and investigated the influence of boron addition on nanotube structure and the mechanical and electrical properties of the resulting B-mixed MWCNT solids. The structure of the prepared material was characterized by scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy-electron energy loss spectroscopy, Raman scattering spectroscopy, and X-ray diffraction, and their mechanical properties and conductivity were measured using a mechanical and Vickers indentation tester and an electric resistor, respectively. It is notable that part of the nanotubes in the B-mixed MWCNT solids solidified at 1800 °C had dramatically changed into rod-like graphitic carbons (RLGCs). The occupancy distribution of RLGCs increased with increasing boron contents. However, boron was not detected in the energy-loss near-edge structure spectrum of RLGCs. Furthermore, RLGCs were not observed in the boron-unmixed sample treated with the same solidified condition, indicating that adding boron causes a remarkable ability to transform the phase of MWCNT. Transformation from MWCNTs to RLGCs resulted in increased specific bending strength and modulus, Vickers hardness, and electrical conductivity of B-mixed MWCNT solids with increasing boron content and solidified temperature.     

Metrological characterization of a Primary Vickers Hardness Standard Machine — NIS Egypt

The main goal of NIS is to provide traceability to international measurement standards to help the Egyptian industry to penetrate world markets. One of the most important fields of metrology is hardness measurements. A Primary Vickers Hardness Standard Machine (PVHM) was designed to improve the capabilities to qualify the primary hardness test blocks locally. The machine has been constructed to perform Vickers hardness test for scales HV10, HV20, HV30, and HV50 with expanded uncertainty of ±1.4 %. This standard machine has been metrologically characterized by NIS. In this paper metrological characterization of the machine will be shown. The characterization includes the methods and results of direct verification of influences parameters (test forces, indentation measuring system, indenter and test cycle time), and a comparison with PTB standard machine.     

Effect of Loading Rate Upon Conventional Ceramic Microindentation Hardness

The world standards for conventional ceramic hardness have varying requirements for control of loading rate during the indentation cycle. A literature review suggests that loading rate may affect measured hardness in some instances. In view of the uncertainty over this issue, new experiments over a range of indentation loading rates were performed on a steel, sintered silicon carbide, and an aluminum oxynitride. There was negligible effect upon Vickers hardness when loading rate was varied by almost four orders of magnitude from approximately 0.03 N/s to 10 N/s.